At least on OpenSUSE 15 I can see this test failing (failed integrations and I was able to reproduce it on the second attempt).
I'll blacklist the test for now and while investigating the problem (Edit: no blacklist, just fixing the bloody wrong code).
|For Gerrit Dashboard: QTBUG-79128|
|275720,2||DTLS auto-test(s) - fix a buggy logic with pending datagrams||5.12||qt/qtbase||Status: MERGED||+2||0|
|276939,2||DTLS auto-test(s) - fix a buggy logic with pending datagrams||5.13||qt/qtbase||Status: MERGED||+2||0|