MB-16452 getting and setting of cluster CA
MB-16452 getting and setting of cluster CA

...with validation of expiration date

Change-Id: I7b62b65c286710baa25369fa0f0eee0991224e1e
Reviewed-on: http://review.couchbase.org/57648
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

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