fix(fix-owner): throw away ENOENTs on chownr

This is a race npm has run into before. I am not sure how to
reproduce such a thing with cacache, but tbh if a directory
or file disappears mid-chown, I could care less?

Furthermore, if the file/directory's existence actually matters,
this will almost certainly error elsewhere. It's fine for us to
drop files on the floor though.

lib/util/fix-owner.js

@@ -27,7 +27,7 @@ function fixOwner (filepath, uid, gid) {
       filepath,
       typeof uid === 'number' ? uid : process.getuid(),
       typeof gid === 'number' ? gid : process.getgid()
-    )
+    ).catch({code: 'ENOENT'}, () => null)
   )
 }