revert : core: Add foreign keys from async_tasks to command_entities

Bare in mind, this is not a pure git revert as DB scripts cannot be
reverted (a script that performs "logical revert" should be added)

Change-Id: Icf54510178460095b09f529b2c5d26eee9efdeec
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>