os/kvstore: trivial portability fixes

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
os/kvstore: remove used var

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
osd: fix type mismatch warning

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Merge pull request #1187 from ceph/port/fixes

portability fixes

Reviewed-by: Sage Weil <sage@inktank.com>