rgw: fixing tempest ObjectTestACLs and ObjectACLsNegativeTest cases

The issue was introduced in ceph@d82ff16
and backported to Squid by: ceph@f0fb48d

As a result rgw couldn't find the correct bucket in case the user from different tenant
was given access to the container using ACL, because rgw started to look inside the
user's tenant, but not the tenant from the request.
This partial revert helps to fix the issue

Signed-off-by: Alexey Odinokov <[email protected]>

Author: aodinokov

src/rgw/rgw_rest_swift.cc

@@ -2947,7 +2947,10 @@ int RGWHandler_REST_SWIFT::postauth_init(optional_yield y)
       && s->user->get_id().id == RGW_USER_ANON_ID) {
     s->bucket_tenant = s->account_name;
   } else {
-    s->bucket_tenant = s->auth.identity->get_tenant();
+    /* tenant must be taken from request. Can't use auth.identity->get_tenant(),
+       because there are cases when users from different tenant may be granted
+       access via ACL to this bucket */
+    s->bucket_tenant = s->user->get_tenant();
   }
   s->bucket_name = t->url_bucket;