Close 3 more fd's that were leaking into child processes.

Child processes now look clean; I can't find any more fd's that are
leaking from the parent to children.

Refs #4550
coll_base_comm_unselect.c: fix memory leaks

Ensure to also OBJ_RELEASE the neightbor and ineighbor modules.

Fixes #4444 (this patch is from that ticket).