res_pjsip_config_wizard: fix test breakage

Fix test breakage caused by not checking for res_pjsip before
calling ast_sip_get_sorcery.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4269/
........

Merged revisions 429653 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@429654 f38db490-d61c-443f-a65b-d21fe96a405b