Improve handling of INET_DIST_INTERFACE option (EJAB-1611)

In old releases, only the erlang format {127,0,0,1} was supported.
Now we support also 127.0.0.1, but we want backwards compatibility.
strings parameters to eldap_utils:get_ldap_attr

we get things like <<"groupname">> from the search,
but this fails to find "groupname"