Redirects requests from /v# to /v#/

Added an APIMapper to catch routemaps when the url is ''
because routes.Mapper returns an error if this is the case
but we want a redirect

Refer to the Nova code at:
https://review.openstack.org/#/c/886/

Change-Id: I74011d14a02a3bc8767fab559ada4c2d82dc5d6e
Fixes: bug #1166957
Merge "Redirects requests from /v# to /v#/"