Signals do not work for pipeline with nested playbin

[lyakhov]

If a pipeline with nested playbin is created via D-Bus call com.ridgerun.gstreamer.gstd.FactoryInterface::Create("( playbin )") gstd reports following errors in stderr:

$ gstd --session

(gstd:7922): GStreamer-CRITICAL **: gst_bus_set_sync_handler: assertion `GST_IS_BUS (bus)' failed

(gstd:7922): GStreamer-CRITICAL **: gst_bus_add_watch_full: assertion `GST_IS_BUS (bus)' failed

As a result, the pipeline is created but signals from com.ridgerun.gstreamer.gstd.PipelineInterface, like EoS, Error, do not work.

This happens in latest gstd from master (https://github.com/RidgeRun/gstd/commit/e8539a0e9413323e3218f183e10e66ca8955ab19) linked with gstreamer 0.10.36 (tried on openSUSE 12.3 and Debian Jessie)