CI: fix commands being stuck problem

[apostasie]

Some commands being tested do deadlock sometimes.
This is particularly true for EL8, for yet undiagnosed reasons.

Because we do not timeout on command execution, the runner will just kill everything, and we do not get any information about which command (nor which test) did actually deadlock, and no logs of course.

We should be able to have some command execution default deadline in place at the test tooling level.
That way, commands being stuck for more than say, 5 minutes, should break and we would report a failed "timed-out test" along with appropriate logs.

@AkihiroSuda can you assign this to me please?