X wcfs: lsof tweaks

- use +D to request recursive search of everything under mntpt
- use -w to avoid seeing many-many warnings in case there are stale FUSE mounts.

wcfs/wcfs_test.py

@@ -119,7 +119,13 @@ def fuse_unmount(mntpt):
         # Print which files are still opened and reraise
         def _():
             print("# lsof %s" % mntpt)
-            subprocess.check_call(["lsof", mntpt])
+            # -w to avoid lots of
+            #  lsof: WARNING: can't stat() fuse.wcfs file system /tmp/wcfs/X
+            #        Output information may be incomplete.
+            # if there are other uncleaned wcfs mountpoints.
+            # (lsof stats all filesystems on startup)
+            # XXX -> better use `fuser -m <mntpt>` (it says it will limit search to files only under mntpt) ?
+            subprocess.check_call(["lsof", "-w", "+D", mntpt])
         defer(_)
         raise