Install OperationCallback for all executed JS scripts

JS doors with the "Use Shell or New Context" option enabled in SCFG and JS
modules installed a global hot key handlers would not automatically terminate
when the user disconnected (and js.auto_terminate was true, the default).
I'm not sure why the operation callback was only installed when scope==NULL
but always installing it fixes the issue with some global hot key modules
and JS doors becoming "zombies" when a user disconnects while running them.