Ensure Asterisk fails TCP/TLS SIP calls when certificate checking fails

Ensure Asterisk fails TCP/TLS SIP calls when certificate checking fails

When placing a call to a TCP/TLS SIP endpoint whose certificate is not
signed by a configured CA certificate, Asterisk would issue a warning
and continue to process the call as if there was not an issue with the
certificate.  Asterisk now properly fails the call if the certificate
fails verification or if the certificate does not exist when
certificate checking is enabled (the default behavior).

(closes issue ASTERISK-20559)
Reported by: kmoore

Review: https://reviewboard.asterisk.org/r/2163/
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Merged revisions 375146 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@375147 65c4cc65-6c06-0410-ace0-fbb531ad65f3