funcs/func_curl: Fix memory leak when CURLOPT channel datastore is destroyed

funcs/func_curl: Fix memory leak when CURLOPT channel datastore is destroyed

When the channel datastore associated with the usage of CURLOPT on a specific
channel is freed, the underlying structure holding the list of options is not
disposed of. This patch properly frees the structure in the datastore .destroy
callback.

ASTERISK-24672 #close
Reported by: Kristian Hogh
patches:
  func_curl-memory-leak.diff uploaded by Kristian Hogh (License 6639)
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Merged revisions 430487 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 430488 from http://svn.asterisk.org/svn/asterisk/branches/13

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@430489 65c4cc65-6c06-0410-ace0-fbb531ad65f3