(Thanks, Dwight, this one look right?)

Make sure we reap our child at cgm_{s,g}et.

Changelog: Fix change in behavior on empty read from the do_cgm_get()
           helper that was spotted by Dwight.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>