debug: ignore wireframe debug drawing for line primitives
debug: ignore wireframe debug drawing for line primitives

If a primitive is already line based then we don't need to do anything
special to draw it in wireframe mode.

Reviewed-by: Neil Roberts <822ec91a7ef82248fd36162ca8ac3283eba70848@linux.intel.com>

gcampax/cogl,djdeath/cogl,djdeath/cogl,gcampax/cogl,gcampax/cogl,djdeath/cogl-android,djdeath/cogl-android,gcampax/cogl,djdeath/cogl-android,djdeath/cogl