Fix refcounting of sip_pvt in test_sip_rtpqos test and unlink it from the list of pvts.

(closes issue ASTERISK-22248)
reported by Corey Farrell
patches:
	test_sip_rtpqos.patch uploaded by Corey Farrell (license #5909)
........

Merged revisions 397112 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@397133 f38db490-d61c-443f-a65b-d21fe96a405b