mon: ceph hashpspool false clears the flag

instead of toggling it.

Signed-off-by: Loic Dachary <loic@dachary.org>
Merge pull request #1237 from dachary/wip-hashpspool

mon: ceph hashpspool false clears the flag

Reviewed-by: Christophe Courtaut <christophe.courtaut@gmail.com>
Reviewed-by: Sage Weil <sage@inktank.com>