osd: noscrub, nodeepscrub osdmap flags

Just add NOSCRUB/NODEEP_SCRUB to OSDMap flags and  allow set/unset

Feature: #4135

Signed-off-by: David Zafman <david.zafman@inktank.com>
Add code to check flag state

Signed-off-by: David Zafman <david.zafman@inktank.com>
Document scrubbing behavior

Signed-off-by: David Zafman <david.zafman@inktank.com>
Merge branch 'wip-4135'

Feature: #4135 - osd: noscrub, nodeepscrub osdmap flags

Reviewed-by: Samuel Just <sam.just@inktank.com>