ext/gio/: Don't use async operations as they require a running main loop.

ext/gio/: Don't use async operations as they require a running main loop.

Original commit message from CVS:
* ext/gio/gstgiobasesink.c: (gst_gio_base_sink_stop),
(gst_gio_base_sink_set_stream):
* ext/gio/gstgiobasesrc.c: (gst_gio_base_src_stop),
(gst_gio_base_src_set_stream):
* ext/gio/gstgiosink.c: (gst_gio_sink_start):
* ext/gio/gstgiosrc.c: (gst_gio_src_start):
Don't use async operations as they require a running main loop.
This makes us block again when closing streams and unable
to mount the enclosing volume of an URI if it isn't yet.