crimson/osd: errororize PG::with_*_obc methods()

crimson/osd: errororize PG::with_*_obc methods()

they all use `seastar::with_lock()` to ensure the obc lock is released
in the error handling path. but we cannot assume that
`seastar::with_lock()` always return `seastar::future<>`, so propogate
the error returned by the function passed to `with_lock()` using
errorator.

Signed-off-by: Kefu Chai <kchai@redhat.com>