safe_asterisk: Cleanup additions to r415132.

* Replaced a stray echo that should've been a message call in
  safe_asterisk. This replaces a conditional log message by a slightly
  different message. Please update your log parsing scripts.
* Made the $NOTIFY mail Subject more verbose by adding the machine name
  and exitstatus.

(Note that a 'make install' still won't overwrite your old safe_asterisk
if it exists. See ASTERISK-21965.)

ASTERISK-23492 #close
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Merged revisions 415521 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 415522 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 415523 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@415524 65c4cc65-6c06-0410-ace0-fbb531ad65f3