HBASE-10583 backport HBASE-8402 to 0.94 - ScanMetrics depends on number of rpc calls to the server. (Liu Shaohui and Himanshu Vashishtha)

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1570756 13f79535-47bb-0310-9956-ffa450edef68