restapi: No trailing / in network labels metadata

The RSDL metadata that describes the operations to add network labels
contains an extra slash at the end of the URL. This makes the RSDL
generator ignore the URL. As a result the RSDL documentation doesn't
contains the headers, and the SDKs are generated incorrectly.

Change-Id: I88781dad71e9dca372de6a84c5c2eb3c8d36c21f
Bug-Url: https://bugzilla.redhat.com/1101531
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>
(cherry picked from commit 8ec2ee221b3c2b3c0f2efa2720d15d082d9287ec)