Fix fs-diff to be have a valid module name

At least mypy would refuse to run on the tests module because of that
invalid name:

  tests$ mypy tests/
  fs-diff is not a valid Python package name

Signed-off-by: Yann Dirson <[email protected]>

Author: ydirson

jobs.py

@@ -429,7 +429,7 @@
         # This test needs 2 hosts that can be from the same pool
         "nb_pools": 1,
         "params": {},
-        "paths": ["tests/fs-diff"],
+        "paths": ["tests/fs_diff"],
     },
 }