ACCUMULO-1947 Remove forcefully setting the logger in a test with no reset after the test is done.
ACCUMULO-1947 Use DfsConfigKeys.DFS_DATANODE_SYNCONCLOSE_KEY instead of the CreateFlag class as a better way to check
whether or not to we warn if the configuration doesn't contain dfs.datanode.synconclose=true
Merge branch '1.5.1-SNAPSHOT' into 1.6.0-SNAPSHOT

Conflicts:
	server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java
	server/tserver/src/test/java/org/apache/accumulo/tserver/log/MultiReaderTest.java
Merge branch '1.6.0-SNAPSHOT'