oeqa/logparser: Fix ptest No-section exception

Occasionally we see:

  File "/media/build/poky/meta/lib/oeqa/runtime/cases/ptest.py", line 27, in test_ptestrunner_expectfail
    self.do_ptestrunner()
  File "/media/build/poky/meta/lib/oeqa/runtime/cases/ptest.py", line 77, in do_ptestrunner
    results, sections = parser.parse(ptest_runner_log)
  File "/media/build/poky/meta/lib/oeqa/utils/logparser.py", line 80, in parse
    self.results[current_section['name']][result.group(1).strip()] = t
KeyError: 'No-section'

which occurs when there are "results" outside the main log section. The strace
tests do then upon failure as they dump logs there.

Add code to avoid the tracebacks and just make them warnings.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>