Fix blind transfers from failing if an 'h' extension is present.

Fix blind transfers from failing if an 'h' extension is present.

This prevents the 'h' extension from being run on the transferee
channel when it is transferred via a native transfer mechanism such
as SIP REFER.

(closes ASTERISK-19173)
Reported by: Ross Beer
Tested by: Kristjan Vrban
Patches:
	ASTERISK-19173 by Mark Michelson (license 5049)

Review: https://reviewboard.asterisk.org/r/1685
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Merged revisions 352199 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 352228 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@352229 65c4cc65-6c06-0410-ace0-fbb531ad65f3