ftrace test failed with Kprobe event auto/manual naming in ubuntu_kernel_selftests

Failure reported in Eoan (5.3.0-43.36, 5.3.0-42.34) s390x:

$ sudo ./ftracetest test.d/kprobe/kprobe_eventname.tc
=== Ftrace unit tests ===
[1] Kprobe event auto/manual naming [FAIL]

# of passed: 0
# of failed: 1
# of unresolved: 0
# of untested: 0
# of unsupported: 0
# of xfailed: 0
# of undefined(test bug): 0

This was not reported before because the ftrace will timeout (bug 1864172)

This failure does not exist on other arches of Eoan.