test: Stop processes of transient user in machines tests
test: Stop processes of transient user in machines tests

When calling TestMachines._testBasic() with a temporary user, libvirtd
often hits an assertion on shutdown:

    Failed to find user record for uid '1002'

and subsequently SIGABRTs. Also, these processes stay around for a while
until systemd cleans them up, which affects the next test. Avoid that by
killing all test user processes at the end.

Turn `createUser()` into a method for that, so that we can use
self.addCleanup().

Also use the more general allow_authorize_journal_messages() in favor of
the custom sudo one.

moraleslazaro/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,deryni/cockpit,garrett/cockpit,mvollmer/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit