[Metricbeat][test failures] master branch got some test failures for the last few days

[v1v]

Tests failures:

• Name: Build and Test / Metricbeat OSS Unit tests / test_system.Test.test_process

Logs

Log details: see https://gist.github.com/v1v/44ea64fc056d4ee392942cd122ec3fc0

Error Message
False is not true : fd not found in any process events
Stacktrace
Traceback (most recent call last):
  File "/usr/lib/python3.6/unittest/case.py", line 59, in testPartExecutor
    yield
  File "/usr/lib/python3.6/unittest/case.py", line 605, in run
    testMethod()
  File "/var/lib/jenkins/workspace/Beats_beats_master/src/github.com/elastic/beats/metricbeat/module/system/test_system.py", line 425, in test_process
    self.assertTrue(found_fd, "fd not found in any process events")
  File "/usr/lib/python3.6/unittest/case.py", line 682, in assertTrue
    raise self.failureException(msg)
AssertionError: False is not true : fd not found in any process events

How to reproduce:

• Spinup an ubuntu-18 VM
• Run the below command

cd metricbeats
mage build unitTest

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)