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


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@409087 f38db490-d61c-443f-a65b-d21fe96a405b