* HADOOP-16948. Support single writer dirs.
* HADOOP-16948. Fix findbugs and checkstyle problems.
* HADOOP-16948. Fix remaining checkstyle problems.
* HADOOP-16948. Add DurationInfo, retry policy for acquiring lease, and javadocs
* HADOOP-16948. Convert ABFS client to use an executor for lease ops
* HADOOP-16948. Fix ABFS lease test for non-HNS
* HADOOP-16948. Fix checkstyle and javadoc
* HADOOP-16948. Address review comments
* HADOOP-16948. Use daemon threads for ABFS lease ops
* HADOOP-16948. Make lease duration configurable
* HADOOP-16948. Add error messages to test assertions
* HADOOP-16948. Remove extra isSingleWriterKey call
* HADOOP-16948. Use only infinite lease duration due to cost of renewal ops
* HADOOP-16948. Remove acquire/renew/release lease methods
* HADOOP-16948. Rename single writer dirs to infinite lease dirs
* HADOOP-16948. Fix checkstyle
* HADOOP-16948. Wait for acquire lease future
* HADOOP-16948. Add unit test for acquire lease failure