Pass 'top' to remove_rule so that rule matching succeeds

When deleting a vpn-site-connection, deleting the nat rule would
fail because it was created with top=True, but top defaults to
'false' in remove_rule and was not being passed. This caused the
rule matching to fail and the rule to not be deleted.

Change-Id: I51012a783314c97e85b31fc8a73be4cbb8ee7dc5
Closes-Bug: #1331839
Merge "Pass 'top' to remove_rule so that rule matching succeeds"