Return empty list if a acl doesn't have any entries
Return empty list if a acl doesn't have any entries

This is similar to bc93ee6352171a324db4914f15df21dd11582337, where
haproxy returns an empty string for acl without entries and returning
one element list with an empty string isn't the right approach.

unixsurfer/haproxyadmin,unixsurfer/haproxyadmin