ifcfg-rh: use nm_utils_ifname_valid() for validating interface-name in reader

Maybe the reader should not try to add its own validation. It
could just read the value, set it in the profile, and let
nm_connection_verify() handle it.

However:

 - in this form the code only logs a warning about invalid setting.
   If we let it come to nm_connection_verify(), the connection profile
   will be entirely rejected. I think this makes sense, because ifcfg
   files may be edited by the user and we don't know what is out there.

 - it's nicer to show a warning that specifically mentions the DEVICE=
   variable. There error message we get from nm_connection_verify()
   is no longer aware of ifcfg peculiarities.

Instead: use the appropriate validation function.

src/settings/plugins/ifcfg-rh/nms-ifcfg-rh-reader.c

@@ -399,7 +399,9 @@ make_connection_setting (const char *file,
 	if (v) {
 		GError *error = NULL;
 
-		if (nm_utils_ifname_valid_kernel (v, &error)) {
+		/* Only validate for NMU_IFACE_KERNEL, because ifcfg plugin anyway
+		 * doesn't support OVS types. */
+		if (nm_utils_ifname_valid (v, NMU_IFACE_KERNEL, &error)) {
 			g_object_set (s_con,
 			              NM_SETTING_CONNECTION_INTERFACE_NAME, v,
 			              NULL);