Shorten the time needed to keep the list lock and alter the cleanup
path to be more of an error path.

Utilize the the virObjectListFree function to handle the calls for
virObjectUnref on each list element and the VIR_FREE of the list
instead of open coding it.

Change the name of the virHashForEach callback to match the name
of the Export function with the Callback added onto it.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>