gst/udp/: Joining a multicast group and setting the loop/ttl properties are totally unrelated tasks are must be separ...

Original commit message from CVS:
* gst/udp/gstmultiudpsink.c: (gst_multiudpsink_init_send),
(gst_multiudpsink_add_internal):
* gst/udp/gstudpnetutils.c: (gst_udp_set_loop_ttl),
(gst_udp_join_group):
* gst/udp/gstudpnetutils.h:
* gst/udp/gstudpsrc.c: (gst_udpsrc_start):
Joining a multicast group and setting the loop/ttl properties are
totally unrelated tasks are must be separated.