ACCUMULO-1328 add SYNC_BLOCK to WAL create calls; warn about synconclose flag when appropriate

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/1.5@1481854 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1328 add SYNC_BLOCK to WAL create calls; warn about synconclose flag when appropriate

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1481867 13f79535-47bb-0310-9956-ffa450edef68