res_calendar_caldav: Add support reading gmail calendar

The response from gmail calendar includes the string name
"caldav:calendar-data". res_calendar_caldav implements
the example included in RFC 4791: string "C:calendar-data".
When reading the calendar, res_calendar_caldav compare the
string and if does not match just discards the event.
This commit compares the response to both strings,
successfully loading gmail calendar events.
Writing to gmail calendar is working prior to this fix.

ASTERISK-26624
Reported by: Eduardo S. Libardi

Change-Id: Ia1eef10552ae616efb645d390f5ffe81260d7d4a