WAL file is still present after clean shutdown/ causes WARN messages in log

[2-Watts]

BUG REPORT

Stack Trace or error message
contractmanager.log

2018/08/07 18:54:08.157988 dependencies.go:247: STARTUP: Logging has started. Siad Version 1.3.3
2018/08/07 18:59:19.572545 writeaheadlog.go:287: WARN: WAL file detected, performing recovery after unclean shutdown.
2018/08/09 14:51:18.106770 dependencies.go:247: STARTUP: Logging has started. Siad Version 1.3.3
2018/08/09 14:56:48.817046 writeaheadlog.go:287: WARN: WAL file detected, performing recovery after unclean shutdown.

Expected Behavior
WAL file should be programmatically erased after correctly being processed.

How to reproduce it (as minimally and precisely as possible)

1. cause to exist after shutdown: ~/Sia/host/contractmanager/contractmanager.wal
   Per my casual and amateur examination; writeaheadlog.go seems to indicate that both the tmp and old .wal files should be deleted automagically after being successfully processed and upon clean shutdown.
   (I am shutting down via './siac stop' and starting via './siad -M cghtw')

Possibly a separate issue, or non-issue at all, is that also 'contractmanager.wal_temp' file remains, after clean shutdown.

Environment

• Sia version: 1.3.3
• OS: Linux Ubuntu 16.04