libs/gst/base/gstcollectpads.c: Unlock mutex when removing an unknown pad.

libs/gst/base/gstcollectpads.c: Unlock mutex when removing an unknown pad.

Original commit message from CVS:
Patch by: Alessandro Decina <alessandro at nnva dot org>
* libs/gst/base/gstcollectpads.c: (gst_collect_pads_remove_pad):
Unlock mutex when removing an unknown pad.
Fixes #343334.
* tests/check/Makefile.am:
* tests/check/libs/collectpads.c: (collected_cb), (push_buffer),
(push_event), (setup), (teardown), (GST_START_TEST),
(gst_collect_pads_suite), (main):
Added collecpads check, disabled for now as check crashes for
some reason.