Ensure the last step in a trace to an action is present
Ensure the last step in a trace to an action is present

* Both states are passed to the find trace function instead
  of only the destination state.
* This also removes the destruction of the levels that took
  place in the action finding code.

To explain: the code with which we skip levels would also
skip the action steps in which we are interested in case
the step is effectively a self-loop. The current code makes
sure both states will occur at the end of the trace being
constructed by passing both states to the find_trace
function and then always adding them to the trace.

The code is a bit more generic and allows an arbitrary
sequence of states being passed.

(Closes #429)

Signed-off-by: Michael Weber <5059b5df59e67be29faa89536427a574a4318434@cs.utwente.nl>

utwente-fmt/ltsmin,utwente-fmt/ltsmin,alaarman/ltsmin,buschko/ltsmin,Sybe/composition,Meijuh/ltsmin,buschko/ltsmin,utwente-fmt/ltsmin,utwente-fmt/ltsmin,trolando/ltsmin,lordqwerty/ltsmin,thedobs/LTSmin,thedobs/LTSmin,vbloemen/ltsmin,vbloemen/ltsmin,Meijuh/ltsmin,thedobs/LTSmin,alaarman/ltsmin,alaarman/ltsmin,buschko/ltsmin,utwente-fmt/ltsmin,trolando/ltsmin,Sybe/composition,vbloemen/ltsmin,trolando/ltsmin,vbloemen/ltsmin,Sybe/composition,lordqwerty/ltsmin,lordqwerty/ltsmin,vbloemen/ltsmin,alaarman/ltsmin,vbloemen/ltsmin,trolando/ltsmin,Meijuh/ltsmin,Meijuh/ltsmin,lordqwerty/ltsmin,Meijuh/ltsmin,alaarman/ltsmin,utwente-fmt/ltsmin,Sybe/composition,vbloemen/ltsmin,thedobs/LTSmin,buschko/ltsmin,alaarman/ltsmin,Meijuh/ltsmin