default xinetd script doesnt allow localhost IPv6 access

the default script used for xinetd for the unix agent does not allow access from localhost IPv6 - this means that for some hosts that prefer using ::1 for localhost instead of 127.0.0.1 that tests will fail and confuse some users

attached is a super quick patch that allows ::1 as well as 127.0.0.1 to connect to observium agent by default

i'm aware that this serves no real use in the real world as your observium server wont be connecting via localhost (unless its looking at itself) but this should stop any complaints of i tried testing this locally but it didnt work