[cbcollect_info] Allow running subset of tasks.
[cbcollect_info] Allow running subset of tasks.

Which is useful for debugging purposes.

Change-Id: Ic71bb76abbd52bdfb22de96ab2970bf6f0a90641
Reviewed-on: http://review.couchbase.org/71672
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server