Partly revert 82bfc77
Partly revert 82bfc77

ScheduledExecutorService#scheduleAtFixedRate already ensures that no two
invocations are running concurrently.

Transcordia/ringojs,Transcordia/ringojs,Transcordia/ringojs,ashwinrayaprolu1984/ringojs,oberhamsi/ringojs,ashwinrayaprolu1984/ringojs,Transcordia/ringojs,ringo/ringojs,ringo/ringojs,ashwinrayaprolu1984/ringojs,ashwinrayaprolu1984/ringojs,ringo/ringojs,ringo/ringojs,oberhamsi/ringojs,oberhamsi/ringojs