ovl: update documentation for unionmount-testsuite

David's tree is no longer maintained, so point to my maintained fork.

Add --verify flag to the run example, which enables all latest features
and provides test coverage for constant st_ino/st_dev.
Signed-off-by: NAmir Goldstein <amir73il@gmail.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Documentation/filesystems/overlayfs.txt

@@ -429,11 +429,12 @@ This verification may cause significant overhead in some cases.
 Testsuite
 ---------
 
-There's testsuite developed by David Howells at:
+There's a testsuite originally developed by David Howells and currently
+maintained by Amir Goldstein at:
 
-  git://git.infradead.org/users/dhowells/unionmount-testsuite.git
+  https://github.com/amir73il/unionmount-testsuite.git
 
 Run as root:
 
   # cd unionmount-testsuite
-  # ./run --ov
+  # ./run --ov --verify