Handle arbitrary number of stats entries from vbucket-seqno stat request

Because there's now 3 stat entries instead of just 2

Change-Id: I4f4a5f3305dd00a31b65731750febeb3f97f8f43
Reviewed-on: http://review.couchbase.org/35171
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>