chan_pjsip: Remove AOR check when dialing and one is specified.

The AOR value may contain the name of an AOR or a full SIP URI.
Checking if the AOR exists can't be done as a result of this.
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Merged revisions 428051 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 428052 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@428053 f38db490-d61c-443f-a65b-d21fe96a405b