mbm: clean up the context on activate_ready

Otherwise the dangling pointer to the context that's being deallocated causes a
crash on spontaneous E2NAP receipt:

  ModemManager[1567]: <info>  [1462468083.031326] [mm-iface-modem.c:1431] __iface_modem_update_state_internal(): Modem /org/freedesktop/ModemManager1/Modem/0: state changed (connecting -> registered)
  ModemManager[1567]: <debug> [1462468083.053745] [mm-port-serial-at.c:459] debug_log(): (ttyACM0): <-- '<CR><LF>*E2NAP: 0,36<CR><LF>'
  ModemManager[1567]: <debug> [1462468083.053857] [mbm/mm-broadband-modem-mbm.c:824] e2nap_received(): disconnected

  (ModemManager:1567): GLib-GIO-CRITICAL **: g_simple_async_result_set_error: assertion 'G_IS_SIMPLE_ASYNC_RESULT (simple)' failed

  Program received signal SIGTRAP, Trace/breakpoint trap.
  g_logv (log_domain=0x7ffff7086798 "GLib-GIO", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7fffffffcda0) at gmessages.c:1046
  1046              g_private_set (&g_log_depth, GUINT_TO_POINTER (depth));
  Missing separate debuginfos, use: debuginfo-install libmbim-1.12.4-2.el7.centos.x86_64 libqmi-1.14.2-1.el7.centos.x86_64
  (gdb) bt
  #0  0x00007ffff6a508c3 in g_logv (log_domain=0x7ffff7086798 "GLib-GIO", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7fffffffcda0) at gmessages.c:1046
  #1  0x00007ffff6a50a3f in g_log (log_domain=log_domain@entry=0x7ffff7086798 "GLib-GIO", log_level=log_level@entry=G_LOG_LEVEL_CRITICAL, format=format@entry=0x7ffff6abe73d "%s: assertion '%s' failed") at gmessages.c:1079
  #2  0x00007ffff6a50a79 in g_return_if_fail_warning (log_domain=log_domain@entry=0x7ffff7086798 "GLib-GIO", pretty_function=pretty_function@entry=0x7ffff7092ce0 <__FUNCTION__.13394> "g_simple_async_result_set_error", expression=expression@entry=0x7ffff7092a40 "G_IS_SIMPLE_ASYNC_RESULT (simple)") at gmessages.c:1088
  #3  0x00007ffff6ff9d3d in g_simple_async_result_set_error (simple=0x7fffe8006e40, domain=297, code=0, format=0x7ffff175b53f "Call setup failed") at gsimpleasyncresult.c:719
  #4  0x00007ffff17569ea in report_connection_status (bearer=0x7fffe4008a40 [MMBroadbandBearerMbm], status=MM_BEARER_CONNECTION_STATUS_DISCONNECTED) at mbm/mm-broadband-bearer-mbm.c:174
  #5  0x000055555559c9f1 in mm_base_bearer_report_connection_status (self=0x7fffe4008a40 [MMBroadbandBearerMbm], status=MM_BEARER_CONNECTION_STATUS_DISCONNECTED) at mm-base-bearer.c:1118
  #6  0x00007ffff17548ed in bearer_list_report_status_foreach (bearer=0x7fffe4008a40 [MMBroadbandBearerMbm], ctx=0x7fffffffd060) at mbm/mm-broadband-modem-mbm.c:805
  #7  0x00007ffff6a45f18 in g_list_foreach (list=<optimized out>, func=0x7ffff17548c9 <bearer_list_report_status_foreach>, user_data=0x7fffffffd060) at glist.c:994
  #8  0x00005555555a224b in mm_bearer_list_foreach (self=0x5555558e0680 [MMBearerList], func=0x7ffff17548c9 <bearer_list_report_status_foreach>, user_data=0x7fffffffd060) at mm-bearer-list.c:146
  #9  0x00007ffff1754a3d in e2nap_received (port=0x5555558e24c0 [MMPortSerialAt], info=0x555555935730, self=0x555555900330 [MMBroadbandModemMbm]) at mbm/mm-broadband-modem-mbm.c:850
  #10 0x000055555563d9fd in parse_unsolicited (port=0x5555558e24c0 [MMPortSerialAt], response=0x7fffe80054f0) at mm-port-serial-at.c:280
  #11 0x0000555555639915 in parse_response_buffer (self=0x5555558e24c0 [MMPortSerialAt]) at mm-port-serial.c:889
  #12 0x0000555555639f0b in common_input_available (self=0x5555558e24c0 [MMPortSerialAt], condition=G_IO_IN) at mm-port-serial.c:1019
  #13 0x0000555555639fc7 in iochannel_input_available (iochannel=0x555555926df0, condition=G_IO_IN, data=0x5555558e24c0) at mm-port-serial.c:1042
  #14 0x00007ffff6a4979a in g_main_context_dispatch (context=0x5555558a4a00) at gmain.c:3109
  #15 0x00007ffff6a4979a in g_main_context_dispatch (context=context@entry=0x5555558a4a00) at gmain.c:3708
  #16 0x00007ffff6a49ae8 in g_main_context_iterate (context=0x5555558a4a00, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3779
  #17 0x00007ffff6a49dba in g_main_loop_run (loop=0x5555558acf10) at gmain.c:3973
  #18 0x000055555558d068 in main (argc=2, argv=0x7fffffffdc38) at main.c:181
  (gdb)

https://bugzilla.redhat.com/show_bug.cgi?id=1333293
https://bugs.freedesktop.org/show_bug.cgi?id=95303

plugins/mbm/mm-broadband-bearer-mbm.c

@@ -317,6 +317,7 @@ activate_ready (MMBaseModem *modem,
      * reset ourselves just in case */
 
     if (!mm_base_modem_at_command_full_finish (modem, res, &error)) {
+        self->priv->connect_pending = NULL;
         g_simple_async_result_take_error (ctx->result, error);
         dial_3gpp_context_complete_and_free (ctx);
         return;