Fix XML encoding of 'identity display' in NOTIFY messages, continued.

Fix XML encoding of 'identity display' in NOTIFY messages, continued.

When r378933 was merged into 1.8, it should have also escaped
remote_display, since it will have the same XML encoding problem when
the caller/callee roles are reversed.

(closes issue ABE-2902)
Reported by: Guenther Kelleter
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Merged revisions 379001 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 379020 from http://svn.asterisk.org/svn/asterisk/branches/11

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@379021 65c4cc65-6c06-0410-ace0-fbb531ad65f3