Refs #155

 - Applicable when using very low signature lifetimes

Refs #155, but does not resolve it

This is only temporary solution until the proper rewrite.

refs #154

There is a merge request waiting for this.

This reverts commit 25e054c4.

ref #103

- DNSSEC planning function no longer cancels the previous signing event, added explicit cancel before calling the function where applicable.
- Removed locks with zd->lock

Refs #151

Refs #254

ref #254

refs #220