Best effort start/stop logrotate.timer systemd service for loganalyzer (#5582)

What is the motivation for this PR?
PR #5414 introduced code to stop/start the logrotate.timer systemd service for
loganalyzer. On older images that do not have the logrotate.timer service,
this operation will fail.

How did you do it?
This change made stopping/starting logrotate.time a best effort operation.

Signed-off-by: Xin Wang <[email protected]>

Author: wangxin

tests/common/plugins/loganalyzer/loganalyzer.py

@@ -32,8 +32,9 @@ def __enter__(self):
         """
         Disable logrotate cron task / systemd timer and make sure the running logrotate is stopped.
         """
-        # Disable logrotate systemd timer
-        self.ansible_host.command("systemctl stop logrotate.timer")
+        # Disable logrotate systemd timer by best effort. The reason is that logrotate.timer service is not
+        # available in older version like 201911.
+        self.ansible_host.command("systemctl stop logrotate.timer", module_ignore_errors=True)
         # Disable logrotate cron task
         self.ansible_host.command("sed -i 's/^/#/g' /etc/cron.d/logrotate")
         logging.debug("Waiting for logrotate from previous cron task or systemd timer run to finish")
@@ -57,8 +58,9 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         """
         # Enable logrotate cron task back
         self.ansible_host.command("sed -i 's/^#//g' /etc/cron.d/logrotate")
-        # Enable logrotate systemd timer
-        self.ansible_host.command("systemctl start logrotate.timer")
+        # Enable logrotate systemd timer by best effort. The reason is that logrotate.timer service is not
+        # available in older version like 201911.
+        self.ansible_host.command("systemctl start logrotate.timer", module_ignore_errors=True)
 
 
 class LogAnalyzerError(Exception):