Workarounds for CMFCore 2.7.0 URLTool REQUEST acquisition issues

After updating Products.CMFCore we had issues on sites where URLTool was registered as ISiteRoot.

In the case of ERP5, we don't really need portal_url.getPortalObject(), this changes to use ERP5Site.getPortalObject(), while at the same time doing something so that portal_url.getPortalObject() also works.

See https://github.com/zopefoundation/Products.CMFCore/pull/126 for more details