Always_failover doesn't require --allow-failover anymore

If an administrator sets always_failover, it means that there is no need
for another explicit approval to failover instead of migrating.

Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>
(cherry picked from commit b5f0b5cc)

Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>