ACCUMULO-1281 flush and compact the !METADATA table after a gc cycle

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/1.5@1468532 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1281 flush and compact the !METADATA table after a gc cycle

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1468533 13f79535-47bb-0310-9956-ffa450edef68