res_pjsip_multihomed: Add logging during startup to aid debugging if local DNS is misbehaving.

This change adds a bit of logging so if the local DNS is misbehaving it is easier
to track down what is going on and where Asterisk may be hanging.

ASTERISK-24438 #close
Reported by: Melissa Shepherd

Review: https://reviewboard.asterisk.org/r/4148/
........

Merged revisions 427300 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@427303 f38db490-d61c-443f-a65b-d21fe96a405b