fix a wrong behavior of alarm timezones in caldav and icalendar when an alarm...

fix a wrong behavior of alarm timezones in caldav and icalendar when an alarm doesnt use utc. This change uses the same timezone from the start time.
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Merged revisions 364163 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@364164 65c4cc65-6c06-0410-ace0-fbb531ad65f3