mgr/dashboard: fix bucket get for s3 account owned bucket

mgr/dashboard: fix bucket get for s3 account owned bucket

**Issue 1:**

When a bucket is created with a user that is owner by the account user,
it fails to fetch the info for the bucket because the owner of that
bucket is considered as owned by the account rather than the user.

dashboard api try to fetch some info for the bucket on the basis of the
bucket owner which in this case fails since its not a real user.

To keep the existing behavior as it is and fix the current issue, I am
doing a check to make sure the user id exists or not. if it doesn't
exist, we goes on to fetch using the dashboard user.

**Issue 2**
Editing the bucket owner by the account is broken. So disabling the
ownership change for the bucket owned by account until we have user
account management for rgw in the dashboard

Fixes: https://tracker.ceph.com/issues/68622
Signed-off-by: Nizamudeen A <nia@redhat.com>