chan_local: Fix local_pvt ref leak in local_devicestate().

chan_local: Fix local_pvt ref leak in local_devicestate().

Regression introduced by ASTERISK-20390 fix.

(closes issue ASTERISK-20769)
Reported by: rmudgett
Tested by: rmudgett
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Merged revisions 376868 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 376869 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 376870 from http://svn.asterisk.org/svn/asterisk/branches/11

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@376871 65c4cc65-6c06-0410-ace0-fbb531ad65f3