handle another^H^H^H^H^H^H^Hmore backwards compatibility regressions

[otakup0pe]

This regression was in the ability to detect whether or not backends have changed or not. There is a likely future optimization in the Backend.fetch function but outside the scope of this PR.

Also added to the diff integration test to make sure we test the NOOP case.

And I have no idea how line 25 of the Makefile ever worked before but it works now (I'm assuming something on the coverage tool changed).

cc @fortinmath

• confirm if this regression is in ldap/userpass
• better test coverage on diff

[otakup0pe]

I think we now have 💯 test coveage of the diff action which is kind of cool. The last pr also fixes #162 (and we've added a smoke test to capture this scenario)

[ericfode]

💯