Revert "core: Add foreign keys from async_tasks to command_entities"

This reverts commit cff91e9211234966692c43a1dfc211858d72a2b7.

Change-Id: I0bedf18c44368297da6201530ea9321496bd5be6
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>