MB-21538: support more flexible stat-based alert messages
MB-21538: support more flexible stat-based alert messages

Allow clients of check_stat_increased to pass in a function
that will format the error message given the name of the bucket,
the stat name and the host.

Change-Id: If5c6ae800b0f957da095272d5a8d8b2415e770c9
Reviewed-on: http://review.couchbase.org/69936
Tested-by: Dave Finlay <7b10a9ed9f70e64c30b07607a671ae61c33f14c8@couchbase.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server