add stacktrace to one xdcr error message

Change-Id: I401840551de1cedb554f158558a916aa5c7276c9
Reviewed-on: http://review.couchbase.org/37935
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
remove some dead code from xdcr

Change-Id: I3198fbf8417651509c4b8789bc53a07e7c50bcb9
Reviewed-on: http://review.couchbase.org/37936
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>