install, cgtop: adjust hashmap_move_one() callers for -ENOMEM possibility

install, cgtop: adjust hashmap_move_one() callers for -ENOMEM possibility

That hashmap_move_one() currently cannot fail with -ENOMEM is an
implementation detail, which is not possible to guarantee in general.
Hashmap implementations based on anything else than chaining of
individual entries may have to allocate.

hashmap_move_one will not fail with -ENOMEM if a proper reservation has
been made beforehand. Use reservations in install.c.

In cgtop.c simply propagate the error instead of asserting.