Ruleflow group rule does not fire when drools-traits is on classpath

When drools-traits is added on the classpath, the provided tests fails on fireAllRules() returning 0 instead of expected 1. The test passes in RHDM/RHPAM 7.8.1 and earlier, the problem was reproduced on master.

If the test describes a behaviour which is now not supported, please let us know, thanks! Otherwise, it seems to be a regression.

I have set the priority to Critical in order to investigate what is going on (if the regression might cause more serious unexpected behaviour), it can be deprioritized if we are sure what it affects.