Allows a file system to provide its own fs-verity implementation but still to hook into the signature check and control file from fs-verity Bug: 160634504 Bug: 170978993 Test: incfs_test running on this + subsequent changes Signed-off-by: Paul Lawrence <paullawrence@google.com> Change-Id: I02020af460d62fa5eb459a083419208e175005e8