HBASE-12740 Improve performance of TestHBaseFsck

Signed-off-by: stack <stack@apache.org>
HBASE-12270 A bug in the bucket cache, with cache blocks on write enabled (Liu Shaohui)
HBASE-12761 On region jump ClientScanners should get next row start key instead of a skip.

Signed-off-by: stack <stack@apache.org>
HBASE-12775: CompressionTest ate my HFile