ast_tls_cert script: Better response for various exit conditions to openssl

(closes issue ASTERISK-20260)
Reported by: Daniel O'Connor
Patches:
	ast_tls_cert-update.diff uploaded by Daniel O'Connor (license 6419)
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Merged revisions 375325 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 375326 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 375327 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@375328 65c4cc65-6c06-0410-ace0-fbb531ad65f3