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

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

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@427303 65c4cc65-6c06-0410-ace0-fbb531ad65f3