Print for how many vbuckets rack constraints are broken.

Two kinds of violations are considered:

  1. Violation is "strict" when master resides on the same rack as any of
  its replicas.

  2. Violation is "weak" when master resides on a different rack, but some
  of the replicas reside on the same rack.

Change-Id: I7bcc52035bc56704cf38e711c82bb69f70bdf3bc
Reviewed-on: http://review.couchbase.org/30857
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>