MB-8363 Set numThreads minimum value to 1.

Change-Id: Ic273744c1076501031af2ba0a9bb6d43368ff23d
Reviewed-on: http://review.couchbase.org/26737
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
MB-8404: prevent replacing 127.0.0.1 in engageCluster reply

That replacement is usually needed for single-node clusters where node
name is 127.0.0.1. And where we cannot send 127.0.0.1 because that
will cause client to try to reach memcached (or moxi) at wrong
address.

But clearly this renaming is not needed in engageCluster which is
intra-cluster API. And also this renaming was actual reason why our
normally very strict pre-join checks failed to detect badness of
trying to join 127.0.0.1.

Change-Id: I34bb56d0018ae626adb8b79f5ac603ef3c434569
Reviewed-on: http://review.couchbase.org/26738
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Merge remote-tracking branch 'couchbase/2.1.0'

* couchbase/2.1.0:
  MB-8404: prevent replacing 127.0.0.1 in engageCluster reply
  MB-8363 Set numThreads minimum value to 1.

Change-Id: I04d350f6f3834f72ecde0e37150ccb65eac97e84