ovs-vsctl: Back out garbage collection changes.

ovs-vsctl: Back out garbage collection changes.

Garbage collection introduced in
c5f341ab193b9126dffef8c77bf8ed35e91290fd changed ovs-vsctl so that
it would allow the garbage collector to reclaim unused tables
instead of manually deleting them itself.  Since garbage collection
runs at transaction completion, undeleted tables would hang around
and could conflict with future actions in a given transaction.
This commit backs out this change.

The following command is an example of something that would have
failed before this commit.

ovs-vsctl -- add-br b \
-- del-br b           \
-- add-br b           \
-- set Interface b other_config:test=test