[lib] fix unblocking
[lib] fix unblocking

See previous commit.

If the user is not a member of the violation group _right now_, even
though they would be at the interval in question, they would not be
unblocked.

The `when` parameter in the check fixes that.

agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft