osd: Only scan for omap corruption once

osd: Only scan for omap corruption once

Before
 	state 2: Can have complete tables (some may be bad)
	state 3: Never had complete tables
After
 	state 2: Can have complete tables (some may be bad)
	state 3 with legacy: Can have complete tables (bad ones are cleared)
	state 3: Never had complete tables

Once OSDs boot with this change you can't downgrade to a previous release.
If someone does downgrade they could have unstable OSDs that hit assert(state.v < 3).
The following command run after shutting down the cluster but before downgrading
ceph packages would be a way to fix this.

ceph-osdomap-tool --omap-path ... --command resetv2

Fixes: http://tracker.ceph.com/issues/21328
Signed-off-by: David Zafman <dzafman@redhat.com>