SDN check: Fix parsing time stamp's time zone

Before this commit, if the control machine and the target machine were in
different time zones and the target machine's time zone were neither UTC
nor GMT, the SDN check would raise a ValueError exception when parsing a
systemd unit's ExecMainStartTimestamp property:

    ValueError: time data 'Tue 2018-08-07 23:09:46 EDT' does not match format '%a %Y-%m-%d %H:%M:%S %Z'

The problem is that Python's strptime cannot reliably parse time zones:
https://bugs.python.org/issue22377

The solution is to drop the time zone prior to parsing the time stamp.

This commit fixes bug 1613752.

https://bugzilla.redhat.com/show_bug.cgi?id=1613752

* roles/openshift_health_checker/openshift_checks/sdn.py
(SDNCheck.save_service_logs): Omit time zone before parsing time stamp.

roles/openshift_health_checker/openshift_checks/sdn.py

@@ -337,8 +337,14 @@ class SDNCheck(OpenShiftCheck):
             self.register_failure('%s is not started.' % service_name)
             return
 
+        # The timestamp should be in the format "%a %Y-%m-%d %H:%M:%S %Z".
+        # However, Python cannot reliably parse timezone names
+        # (see <https://bugs.python.org/issue22377>), so we must drop the
+        # timezone name before parsing the timestamp.
+        start_timestamp = ' '.join(start_timestamp.split()[0:3])
+
         since_date = datetime.datetime.strptime(start_timestamp,
-                                                '%a %Y-%m-%d %H:%M:%S %Z')
+                                                '%a %Y-%m-%d %H:%M:%S')
         until_date = since_date + datetime.timedelta(minutes=5)
         since = since_date.strftime(time_fmt)
         until = until_date.strftime(time_fmt)