novatel: obtain MMPortProbe from GTask source object

The MMPortProbe object is already referenced by the GTask object for
custom init. Instead of keeping another reference of MMPortProbe in the
CustomInitContext, this patch changes the code to simply obtain it from
the source object of GTask.

See https://lists.freedesktop.org/archives/modemmanager-devel/2017-April/004420.html

plugins/novatel/mm-common-novatel.c

@@ -20,7 +20,6 @@
 /* Custom init */
 
 typedef struct {
-    MMPortProbe *probe;
     MMPortSerialAt *port;
     guint nwdmat_retries;
     guint wait_time;
@@ -30,7 +29,6 @@ static void
 custom_init_context_free (CustomInitContext *ctx)
 {
     g_object_unref (ctx->port);
-    g_object_unref (ctx->probe);
     g_slice_free (CustomInitContext, ctx);
 }
 
@@ -84,6 +82,7 @@ static void
 custom_init_step (GTask *task)
 {
     CustomInitContext *ctx;
+    MMPortProbe *probe;
 
     ctx = g_task_get_task_data (task);
 
@@ -96,8 +95,10 @@ custom_init_step (GTask *task)
         return;
     }
 
+    probe = g_task_get_source_object (task);
+
     /* If device has a QMI port, don't run $NWDMAT */
-    if (mm_port_probe_list_has_qmi_port (mm_device_peek_port_probe_list (mm_port_probe_peek_device (ctx->probe)))) {
+    if (mm_port_probe_list_has_qmi_port (mm_device_peek_port_probe_list (mm_port_probe_peek_device (probe)))) {
         mm_dbg ("(Novatel) no need to run custom init in (%s): device has QMI port",
                 mm_port_get_device (MM_PORT (ctx->port)));
         g_task_return_boolean (task, TRUE);
@@ -142,7 +143,6 @@ mm_common_novatel_custom_init (MMPortProbe *probe,
     GTask *task;
 
     ctx = g_slice_new (CustomInitContext);
-    ctx->probe = g_object_ref (probe);
     ctx->port = g_object_ref (port);
     ctx->nwdmat_retries = 3;
     ctx->wait_time = 2;