res_pjsip_endpoint_identifier_ip: Add 'show identify(ies)' cli commands

While troubleshooting other things I realized there were no pjsip cli
commands for identify.  This patch adds them.  It also also fixes a
reference leak when a 'show endpoint' displayed identifies and properly
sets the return code if load_module can't allocate a cli formatter structure.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4212/



git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@428725 f38db490-d61c-443f-a65b-d21fe96a405b