This issue can now be spotted on B-gke-4.15 (4.15.0-1049.52)
For the test log, it looks like this happened before (the one marked with no ltp test history):
* 4.15.0-1049.52-gke - no ltp test history
* 4.15.0-1046.49-gke - no ltp test history
* 4.15.0-1045.48-gke - no ltp test history
* 4.15.0-1042.44-gke - no ltp test history
* 4.15.0-1041.43-gke - LTP well tested
* 4.15.0-1040.42-gke - no ltp test history
* 4.15.0-1038.40-gke - LTP well tested
* 4.15.0-1037.39-gke - LTP well tested
* 4.15.0-1035.37-gke - LTP well tested
This issue can now be spotted on B-gke-4.15 (4.15.0-1049.52)
For the test log, it looks like this happened before (the one marked with no ltp test history):
* 4.15.0-1049.52-gke - no ltp test history
* 4.15.0-1046.49-gke - no ltp test history
* 4.15.0-1045.48-gke - no ltp test history
* 4.15.0-1042.44-gke - no ltp test history
* 4.15.0-1041.43-gke - LTP well tested
* 4.15.0-1040.42-gke - no ltp test history
* 4.15.0-1038.40-gke - LTP well tested
* 4.15.0-1037.39-gke - LTP well tested
* 4.15.0-1035.37-gke - LTP well tested
So this is not a regression for GKE this time.