add collector logger
add collector logger

Change-Id: I2ab0a91b07c3a29b74e0ddb0161528706f745439
Reviewed-on: http://review.couchbase.org/25484
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

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