MB-9826: use new connection for remote cluster/bucket check

I.e. so that we can detect certificate mismatch.

Note that it does not prevent us from reusing previously established
connections for data traffic. But that's relatively fine and a
different problem anyways (i.e. solving it requires making sure _all
cluster nodes_ stopped using connections established using old
certificate).

Change-Id: I63ddc669a236be0665811f717718e0b5ecaf797d
Reviewed-on: http://review.couchbase.org/31695
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>