MB-12750 handle potential "cancelXCDR" typo in request path

this was original typo in rest api's and potentially some clients
still use this entry point

Change-Id: Ibb0e0198a68292e5f0c8de9a8d298e65573fc9df
Reviewed-on: http://review.couchbase.org/44298
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>