noip.c (fixup_client_socket): Reorder the preflight checks.

noip.c (fixup_client_socket): Reorder the preflight checks.

Superficially, it looks as if `acl_allows_p' will be cheaper than
`real_getsockname'.  But actually, if `acl_allows_p' passes the remote
address then we'll end up doing a `real_getsockname' anyway in order to
decide whether we need to substitute an unfaked socket, so this is a
false economy.

This shouldn't actually change the effective behaviour, but it will
improve performance -- not that this hack is especially performance
critical.