Drop broute from ebtables_dump

This table is no longer present on most installations, drop it
from the list to avoid error messages during log collection
that people mistake to be the real error why devstack is failing.

This may lose some debugging information in edge cases, but I
think the improvement of the general user experience is more
important.

Change-Id: Ibb9b247a018a788c8c4b40487762319fe470bf0f
Closes-Bug: 1885198

Author: jharbott

tools/worlddump.py

@@ -134,7 +134,7 @@ def disk_space():
 
 
 def ebtables_dump():
-    tables = ['filter', 'nat', 'broute']
+    tables = ['filter', 'nat']
     _header("EB Tables Dump")
     if not _find_cmd('ebtables'):
         return