Fix memory stomping bug in astman.

This memset complained in dev mod on my Ubuntu box. The memset is both
unnecessary and dangerous. At this point, m hasn't been initialized
yet, so the memset will write off to whatever address happens to be
on the stack at the time.
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Merged revisions 409077 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 409083 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 409087 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@409091 65c4cc65-6c06-0410-ace0-fbb531ad65f3