fix duplicate default collectors
fix duplicate default collectors

Change-Id: Ie8737cc13cd4e56893085b110a8051a57a7bdf8f
Reviewed-on: http://review.couchbase.org/25568
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Pavel Paulau <dd88eded64e90046a680e3a6c0828ceb8fe8a0e7@gmail.com>

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