fix some additional program refcounting bugs

cherry-picked from master
diff --git a/src/mesa/shader/shader_api.c b/src/mesa/shader/shader_api.c
index f12fa28..2b3dbff 100644
--- a/src/mesa/shader/shader_api.c
+++ b/src/mesa/shader/shader_api.c
@@ -243,10 +243,8 @@
       _mesa_free((void *) sh->Source);
    if (sh->InfoLog)
       _mesa_free(sh->InfoLog);
-   for (i = 0; i < sh->NumPrograms; i++) {
-      assert(sh->Programs[i]);
-      ctx->Driver.DeleteProgram(ctx, sh->Programs[i]);
-   }
+   for (i = 0; i < sh->NumPrograms; i++)
+      _mesa_reference_program(ctx, &sh->Programs[i], NULL);
    if (sh->Programs)
       _mesa_free(sh->Programs);
    _mesa_free(sh);