OpenSubdiv: initialize in background-mode

Previously this was initialized with OpenGL, however this uses a
more proper/complete implementation it is not only for OpenGL.

source/blender/windowmanager/intern/wm_init_exit.c

@@ -190,8 +190,6 @@ void WM_init_opengl(void)
 
   GPU_pass_cache_init();
 
-  BKE_subdiv_init();
-
   opengl_is_init = true;
 }
 
@@ -323,6 +321,8 @@ void WM_init(bContext *C, int argc, const char **argv)
     UI_init();
   }
 
+  BKE_subdiv_init();
+
   ED_spacemacros_init();
 
   /* note: there is a bug where python needs initializing before loading the