RGW Swift API: add support for URL schema compatible with Swift
RGW currently supports multiple accounts (unfortunately without separate namespaces - see #5073). The account name is obtained from auth mechanism and URL doesn't contain it. This introduces incopability with OpenStack Object Storage API which says:
The public URL that is the HTTP endpoint from where you can access Object Storage. It includes the Object Storage API version number and your account name. For example, https://220.127.116.11/v1/my_account.
There is a configuration option rgw_swift_tenant_name, but it is still not enough due to the lack of support for multiple accounts in that way.