Ensure DirectoryStream is closed promptly

Ensure DirectoryStream is closed promptly

From the javadoc for Files.list:

"The returned stream encapsulates a DirectoryStream. If timely disposal
of file system resources is required, the try-with-resources construct
should be used to ensure that the stream's close method is invoked
after the stream operations are completed."

This is the only call to Files#newDirectoryStream that is not already in
a try-with-resources.

Change-Id: I91e6c56b5d74e8435457ad6ed9e6b4b24d2aa14e