st/mesa: initialize key in st_vp_varient

This fixes endless vertex shader recompilations in find_translated_vp
if the shader contains an edge flag output.

NOTE: This is a candidate for the 7.9 branch.

Signed-off-by Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_program.c

@@ -216,6 +216,8 @@ st_translate_vertex_program(struct st_context *st,
       return NULL;
    }
 
+   vpv->key = *key;
+
    vpv->num_inputs = stvp->num_inputs;
    num_outputs = stvp->num_outputs;
    if (key->passthrough_edgeflags) {