MB-100: fix unreaable XDCR trace

The original trace was modified in recent commits but the
XMem remote info is dumped incorrectly and unreadable. This
commit will create a readable string for XMmem remmote. E.g,

(target node: 10.3.121.123:11210, target bucket: default)

Change-Id: Ie16792077100ebc96206bbc4449fe9c9858b3bfa
Reviewed-on: http://review.couchbase.org/28537
Tested-by: Junyi Xie <junyi.couchbase@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>