ideas for https://github.com/teemtee/tmt/issues/2772

[skycastlelily]

for artemis/testcloud guest,both tmt clean guests and tmt clean runs works as expected if you run tmt clean guests first,but users will see the confusing output as reported,I guess tmt could
1)warn users that the workdir has already been removed,so nothing can be done for tmt clean guests,
2) add an option for clean runs to let user choose if they want to clean the related guest or not

@happz @psss @lukaszachy What do you think?:)

[skycastlelily]

Code may help you reviewers see the problem clearly,so here are the two merge requests
for 1) #2805
for2) #2806 I'm thinking to add --how,-- keep options after this one is merged to avoid sending not clear merge request:)