Make ifaces_get work with dynamic no_rings

Commit which added number of addresses to srp_address structure didn't
count with totemsrp_ifaces_get where whole structure was copied instead
of addresses only. This is now fixed.

Also to make API totempg forward compatible, size of interfaces array
must be passed to ifaces_get like functions to prevent memory overwrite.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>