jobs: use job locks also in the unit tests

jobs: use job locks also in the unit tests

Add missing job synchronization in the unit tests, with
explicit locks.

We are deliberately using _locked functions wrapped by a guard
instead of a normal call because the normal call will be removed
in future, as the only usage is limited to the tests.

In other words, if a function like job_pause() is/will be only used
in tests to avoid:

WITH_JOB_LOCK_GUARD(){
    job_pause_locked();
}

then it is not worth keeping job_pause(), and just use the guard.

Note: at this stage, job_{lock/unlock} and job lock guard macros
are *nop*.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220926093214.506243-10-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>