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/1099415
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>