Blocked revisions 370361

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Free any datastores attached to dummy channels.

Revision 370205 added the use of a datastore attached to a dummy channel to
resolve a memory leak, but ast_dummy_channel_destructor() in this branch did
not free datastores, resulting in a continued (but slightly smaller) memory
leak. This patch backports the change to free said datastores from the Asterisk
trunk.

(related to issue AST-916)
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Merged revisions 370360 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@370362 65c4cc65-6c06-0410-ace0-fbb531ad65f3