Update documentation for leastrecent strategy.

Update documentation for leastrecent strategy.

In queues.conf.sample the leastrecent strategy was incorrectly described. Now updated
to reflect how the strategy actually checks peers.

(closes issue ASTERISK-17854)
Reported by: Sebastian Denz
Patches:
     queues.conf-doc_issue.patch (License #6139)
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Merged revisions 343047 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 343048 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@343049 65c4cc65-6c06-0410-ace0-fbb531ad65f3