Sort the output of 'database show' by key.

This more closely mimics the behavior of 'database show' before the conversion
to sqlite3.
........

Merged revisions 350938 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@350939 65c4cc65-6c06-0410-ace0-fbb531ad65f3