CryptoOutputStream should implement StreamCapabilities

Running some tests with HBase on HDFS with encryption, we noticed that CryptoOutputStream doesn't implement StreamCapabilities.

Specifically, we have a HdfsDataOutputStream wrapping a CryptoOutputStream. The calls to hasCapability on the HDOS will always return false, even though the COS could be wrapping something that supports it, as evidenced by the implementation of hsync and hflush here.