msg/msg_types: entity_addrvec_t: fix decode on big-endian hosts

msg/msg_types: entity_addrvec_t: fix decode on big-endian hosts

When decoding an entity_addrvec_t with marker 1, we just have
a single (non-legacy) entity_addr_t.  This should be decoded
exactly the same as done by entity_addr_t::decode, but it
currently is not.  Specifically, the sa_family member of
the sockaddr is not converted from the on-wire little-endian
format to host byte order (as done by entity_addr_t::decode).

Fixed by using the same code as in entity_addr_t::decode.

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>