mem: fix rte_malloc(SOCKET_ID_ANY), try to allocate on other nodes

Before this patch, rte_malloc(SOCKET_ID_ANY) was equivalent to
rte_malloc(this_socket). If the user specifies SOCKET_ID_ANY, it means that
memory can be allocated on any socket. So fix the behavior of rte_malloc() in
order to do that. The current CPU socket is still the default, but if it fails,
other sockets are tested.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>