osd/scrub: operator abort: (not) handling in-the-mail scrubs

osd/scrub: operator abort: (not) handling in-the-mail scrubs

Fix on_operator_abort_scrub() to handle the case where
the operator-initiated abort request arrives while the
'start scrub' message is still in the queue (i.e. -
is_queued_or_active() is true, but is_scrub_active()
is false).

Unlike our handling of, for example, FullReset in
PrimaryIdle::clear_state(), here we choose to ignore
the request:
Considering the added complexity to the FSM versus
the minimal benefit, it is better to just ignore this
very rare case, leaving it to the operator to re-issue
the abort command if needed.

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>