MB-8748 script to reset admin password

- /couchbase/install/bin/cbreset_password
- doesn't work on the server started by cluster_run
  because dump_guts script doesn't work on it

Change-Id: Ic2e62930a2da87289ab518459e6fbc723b794774
Reviewed-on: http://review.couchbase.org/27982
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>