base-manager: plug memleak

Don't g_strdup() the physdev string to store it in the hash table; instead store
the original string right away as it is already created with g_strdup_printf().

Reported by: Yunlian Jiang <yunlian@chromium.org>

https://code.google.com/p/chromium/issues/detail?id=515929

src/mm-base-manager.c

@@ -749,9 +749,7 @@ handle_set_profile (MmGdbusTest *skeleton,
     /* Create device and keep it listed in the Manager */
     physdev = g_strdup_printf ("/virtual/%s", id);
     device = mm_device_virtual_new (physdev, TRUE);
-    g_hash_table_insert (self->priv->devices,
-                         g_strdup (physdev),
-                         device);
+    g_hash_table_insert (self->priv->devices, physdev, device);
 
     /* Grab virtual ports */
     mm_device_virtual_grab_ports (device, (const gchar **)ports);