[Tachyon-26] test UnderFileSystem.get() code path in Glusterfs Cluster.

Fix the dependency issue in gluster test profile;
Update gluster test instruction in glusterfs setup document.

Signed-off-by: rootfs <hchen@redhat.com>
Yes, you are absolutely right on the steps. All ufs test files go to tachyon_test folder. It is not configurable.