Fix stats seqno test on centos

The issue here is that we need to get our stat for the vb uuid as
an unsigned long long. If we get it as an int the the stat can be
truncated and cause the test to fail.

Change-Id: Ieb523432d4d51360d63561ee4eb5c4be41422c51
Reviewed-on: http://review.couchbase.org/32534
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>