gst: ensure GStreamer initialization debug message is displayed
gst: ensure GStreamer initialization debug message is displayed

The GST_INFO ("initialized GStreamer succesfully") is currently at the end of
gst_init_check which isn't guaranteed to be run since GStreamer can be
initialized by using init_pre and init_post directly from GOptionContext like
gst-launch does. Ensure this message is displayed by moving it to init_post.

krichter722/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,centricular/gstreamer,jpxiong/gstreamer,mparis/gstreamer,mparis/gstreamer,jpxiong/gstreamer,centricular/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,centricular/gstreamer,mparis/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,centricular/gstreamer,mparis/gstreamer