Fix X-Backend-Storage-Policy-Index requests

The reconciler needs to make PUT/GET requests to specific Storage Policies
despite the cached value of the container_info.

The existing implementation was pulling the request header after it had
already selected the ring and was placing objects on the wrong devices.

Change-Id: I2f92b9ddc1179e0223bcb33fc4cfead50db0ae78
Merge "Fix X-Backend-Storage-Policy-Index requests" into feature/ec