gst/base/gstbasesrc.c: Remove implicit cast from gboolean to GstElementStateReturn; make sure we still return failure...

Original commit message from CVS:
* gst/base/gstbasesrc.c: (gst_basesrc_change_state):
Remove implicit cast from gboolean to GstElementStateReturn;
make sure we still return failure in paused => ready case if
the parent class fails to change state and our own stop
vfunc succeeds.