A typo in the lvs-masquerade script prevented the deletion of the
'ip6-udp-masq' nftables chain when stopping a network interface.
The name of the chain should be 'ip6-udp-masq' instead of 'ip-udp-masq'
The bug had no impacts on the loadbalancers but it displayed an error
message in the logs.
Change-Id: Iba07010b63771aafa1db224dbd0e0c97925d6173