rgw: fix printing wrong X-Storage-Url in Swift's TempAuth.

rgw: fix printing wrong X-Storage-Url in Swift's TempAuth.

If the option "rgw_swift_account_in_url" is being set to true,
both user and subuser IDs will be present in the X-Storage-Url
header generated by the implementation of Swift API's TempAuth.
This patch rectifies this behavior and makes that only the user
identifier will be placed there.

Fixes: http://tracker.ceph.com/issues/15667
Signed-off-by: Radoslaw Zarzynski <rzarzynski@mirantis.com>