tests: fix various object leaks cont
tests: fix various object leaks cont

Do not use self.fail when handling exception - this will keep exception
object referenced, which in turn have reference to domain object (via
traceback).

QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin