MB-100: removed passing UserPassword to pool_info functions

We really only need to know if request is executed under admin or not.

Change-Id: Idf921acfd5f4457bab2bfc69b3df26f9f408fb82
Reviewed-on: http://review.couchbase.org/27951
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>