Revert "MB-10415 hashing of admin and read only user passwords"

This reverts commit eb58ee65b3338f655ebac3b68dccdd18ee8b3ec1.

Change-Id: I41aed3699c0924bc146d15214fc1d04562730309
Reviewed-on: http://review.couchbase.org/35076
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>