rgw: failed resharding clears resharding status from shard heads

rgw: failed resharding clears resharding status from shard heads

Previously, when resharding failed, we restored the shard status on
the bucket info object. However the status on each of the shards was
left indicating a reshard was underway. This prevented some write
operations from taking place, as they would wait for resharding to
complete. This adds the missing functionality. It also makes the
functionality available to other classes via static functions in
RGWBucketReshard.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>
(cherry picked from commit 4577801271454b147cb3b1f3169d268d1c14948b)