sierra: fix ICCID requests

Depending on when the core requested the ICCID, the port may or may
not be open.  Stuff that needs an open serial port needs to make sure
that the port gets opened itself.

plugins/mm-modem-sierra-gsm.c

@@ -293,26 +293,33 @@ get_sim_iccid_done (MMAtSerialPort *port,
     }
 
 done:
+    mm_serial_port_close (MM_SERIAL_PORT (port));
     mm_callback_info_schedule (info);
 }
 
 static void
 get_sim_iccid (MMGenericGsm *modem,
                MMModemStringFn callback,
-               gpointer user_data)
+               gpointer callback_data)
 {
     MMAtSerialPort *port;
     MMCallbackInfo *info;
+    GError *error = NULL;
 
-    info = mm_callback_info_string_new (MM_MODEM (modem), callback, user_data);
+    port = mm_generic_gsm_get_best_at_port (modem, &error);
+    if (!port)
+        goto error;
 
-    port = mm_generic_gsm_get_best_at_port (modem, &info->error);
+    if (!mm_serial_port_open (MM_SERIAL_PORT (port), &error))
-    if (!port) {
+        goto error;
-        mm_callback_info_schedule (info);
-        return;
-    }
 
+    info = mm_callback_info_string_new (MM_MODEM (modem), callback, callback_data);
     mm_at_serial_port_queue_command (port, "!ICCID?", 3, get_sim_iccid_done, info);
+    return;
+
+error:
+    callback (MM_MODEM (modem), NULL, error, callback_data);
+    g_clear_error (&error);
 }
 
 /*****************************************************************************/