log post request errors in metadata client
log post request errors in metadata client

Change-Id: Id14f7f00ef08d4188eccf29abebef9f3b8e0433c
Reviewed-on: http://review.couchbase.org/25488
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

pavel-paulau/cbagent,mikewied/cbagent,couchbase/cbmonitor,couchbase/cbmonitor,vmx/cbagent,couchbase/cbagent