ubuntu_kernel_selftests tend to timeout on 5.0 kernels

Issue spotted on the following kernels:
  * linux-oracle 5.0.0-1010.15~18.04.1
  * linux-oracle 5.0.0-1010.15
  * linux-gcp 5.0.0-1029.30
  * linux-gke 5.0.0-1029.30~18.04.1

The jenkins job will timeout with the 4hr threshold, however it seems that the test itself has finished in 45 minutes

This issue is preventing the report being generated. It will be a failed-to-build job on jenkins server.

This is the end of the report on jenkins server:

 [77] (instance) event trigger - test histogram modifiers [PASS]
 [78] (instance) event trigger - test multiple histogram triggers [PASS]
 [79] (instance) trace_marker trigger - test snapshot trigger [PASS]

 # of passed: 76
 # of failed: 0
 # of unresolved: 2
 # of untested: 0
 # of unsupported: 1
 # of xfailed: 0
 # of undefined(test bug): 0
 not ok 1..1 selftests: ftrace: ftracetest [FAIL]
 make[1]: Leaving directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/ftrace'
 make: Leaving directory '/home/ubuntu/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests'
 Exception escaping from test:

 child process failed
 Traceback (most recent call last):
   File "/home/ubuntu/autotest/client/parallel.py", line 25, in fork_start
     l()
   File "/home/ubuntu/autotest/client/job.py", line 505, in <lambda>
     l = lambda: test.runtest(self, url, tag, args, dargs)
   File "/home/ubuntu/autotest/client/test.py", line 125, in runtest
     job.sysinfo.log_after_each_iteration)
   File "/home/ubuntu/autotest/client/shared/test.py", line 913, in runtest
     mytest._exec(args, dargs)
   File "/home/ubuntu/autotest/client/shared/test.py", line 411, in _exec
     _call_test_function(self.execute, *p_args, **p_dargs)
   File "/home/ubuntu/autotest/client/shared/test.py", line 823, in _call_test_function
     return func(*args, **dargs)
   File "/home/ubuntu/autotest/client/shared/test.py", line 291, in execute
     postprocess_profiled_run, args, dargs)
   File "/home/ubuntu/autotest/client/shared/test.py", line 212, in _call_run_once
     self.run_once(*args, **dargs)
   File "/home/ubuntu/autotest/client/tests/ubuntu_kernel_selftests/ubuntu_kernel_selftests.py", line 171, in run_once
     raise error.TestError('Test failed for ' + test_name)
 TestError: Test failed for ftrace
   ERROR ubuntu_kernel_selftests.ftrace ubuntu_kernel_selftests.ftrace timestamp=1579063771 localtime=Jan 15 04:49:31 Test failed for ftrace
  END ERROR ubuntu_kernel_selftests.ftrace ubuntu_kernel_selftests.ftrace timestamp=1579063771 localtime=Jan 15 04:49:31
 Persistent state client._record_indent now set to 1
 Persistent state client.unexpected_reboot deleted
 END GOOD ---- ---- timestamp=1579063771 localtime=Jan 15 04:49:31
 Persistent state client._record_indent now set to 0
 Report successfully generated at /home/ubuntu/autotest/client/results/default/job_report.html
Build timed out (after 240 minutes). Marking the build as aborted.