osd: initialize new_state field when we use it

If we use operator[] on a new int field its value is undefined; avoid
reading it or using |= et al until we initialize it.

Fixes: #4967
Backport: cuttlefish, bobtail
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: David Zafman <david.zafman@inktank.com>