rgw: save bucket instance xattrs when resharding cancelled

rgw: save bucket instance xattrs when resharding cancelled

There appears to be a long-standing bug in RGW such that when
resharding is cancelled and the bucket instance is updated to reflect
the new resharding status, the xattrs were lost. The xattrs are used
to store metadata such as ACLs and LifeCycle policies.

This commit makes sure that all call paths that lead to a cancelled
reshard provide the xattrs, so they can be included when the bucket
instance info is updated.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>