Adapt maven path search for files and dirs

The "-f" maven param can specify both a directory, in which case it
will look for "pom.xml" in the directory, or a specific file. The
original version of this search was only compatible with directories
that contain a pom.xml file.

Change-Id: I81ab161f3156fc2159a4b7ca9ca084a0f82da795
Signed-off-by: Eric Ball <eball@linuxfoundation.org>