metadata: fix cache check? (TODO)

Noticed when reviewing commits after the news issue
(see referenced PR).

This should be equivalent but I think it's
more readable this way (ditching the
negatives).

Fixes: 9e24d01
See: gentoo#853
Signed-off-by: Sam James <sam@gentoo.org>

lib/portage/metadata.py

@@ -187,10 +187,10 @@ def sigwinch_handler(signum, frame):
                         # We don't want to skip the write unless we're really
                         # sure that the existing cache is identical, so don't
                         # trust _mtime_ and _eclasses_ alone.
-                        cache_is_identical = (
-                            True for k in auxdbkeys if dest.get(k, "") != src.get(k, "")
+                        cache_is_identical = all(
+                            dest.get(k, "") == src.get(k, "") for k in auxdbkeys
                         )
-                        if any(cache_is_identical):
+                        if not cache_is_identical:
                             dest = None
                 if dest is not None:
                     # The existing data is valid and identical,