Fix the iomux_add/clear events. Also properly remember

the events in the IOMuxFD

src/iomux_impl.c

@@ -151,6 +151,7 @@ int iomux_update_events(struct IOMux *mux, struct IOMuxFD *fd, unsigned int what
     if (fd->what != what) {
         fd->what = what;
         rc = mux->ops.update_events_impl(mux, fd);
+        fd->what = what;
     }
 
     return rc;