pywalt: fix stuck communication am: de48cf557f am: 842e8b8860 am: 26b4ade211

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/walt/+/12239743

Change-Id: Icadf1cf1a5a4e0f09a8ee7e63976d1035749b3bb