This reverts commit 7f6729de.

ZODB has been switched to ZODB4 in 447b27e6 (Switch from ZODB3 (3.10.7)
to ZODB (4.4.4)) including raising transaction version requirement to
1.7.0 so we can try to introduce zodbtools one more time.

/proposed-for-review-on nexedi/slapos!121