HBASE-12274 Race between RegionScannerImpl#nextInternal() and RegionScannerImpl#close() may produce null pointer exception
HBASE-12261 Add checkstyle to HBase build process

Conflicts:
	dev-support/test-patch.sh
	pom.xml
HBASE-12264 ImportTsv should fail fast if output is not specified and table does not exist (Ashish)