qa/suites/rados/dashboard: ignore MON_DOWN

qa/suites/rados/dashboard: ignore MON_DOWN

This warning is expected during:

2020-10-27T16:29:40.549+0000 7fa1f0927700 10 mon.c@2(peon) e1 handle_auth_request haven't formed initial quorum, EBUSY

and is cleared after:

2020-10-27T16:29:42.597+0000 7fe7b3ada700  7 mon.a@1(peon).log v7 update_from_paxos applying incremental log 7 2020-10-27T16:29:42.319274+0000 mon.b (mon.0) 76 : cluster [INF] mon.b is new leader, mons b,a,c in quorum (ranks 0,1,2)
2020-10-27T16:29:42.597+0000 7fe7b3ada700  7 mon.a@1(peon).log v7 update_from_paxos applying incremental log 7 2020-10-27T16:29:42.326711+0000 mon.b (mon.0) 82 : cluster [INF] Health check cleared: MON_DOWN (was: 1/3 mons down, quorum b,a)

Signed-off-by: Neha Ojha <nojha@redhat.com>