device-crash-test: Python 3 compatibility fix

Restrict whitelist entry stats in debug mode to be sorted only by
"count", since Python 3 does not implicitly support comparing
dictionaries.

Signed-off-by: Nisarg Shah <nshah@disroot.org>
Message-Id: <20190116183358.30287-1-nshah@disroot.org>
[ehabkost: removed 2 unnecessary hunks from patch]
[ehabkost: edited commit message]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

scripts/device-crash-test

@@ -557,7 +557,8 @@ def main():
         logger.info("Skipped %d test cases", skipped)
 
     if args.debug:
-        stats = sorted([(len(wl_stats.get(i, [])), wl) for i, wl in enumerate(ERROR_WHITELIST)])
+        stats = sorted([(len(wl_stats.get(i, [])), wl) for i, wl in
+                         enumerate(ERROR_WHITELIST)], key=lambda x: x[0])
         for count, wl in stats:
             dbg("whitelist entry stats: %d: %r", count, wl)