avoid divide by 0 in compaction_daemon if there are no vbuckets

Change-Id: I6abe8155655264cfe247b8e4a1f403b7a746883b
Reviewed-on: http://review.couchbase.org/35306
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
recognize flow control commands for purpose of debugging upr

Change-Id: I2322522eed2c73a81468cc92eb3603192c51fb97
Reviewed-on: http://review.couchbase.org/35307
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>