Add safe_reload for config_reload in test_syslog_srouce_ip (sonic-net#16969)

What is the motivation for this PR?
Without safe_reload, it's not enough time to wait system healthy. safe_reload will check critical services after reload.

How did you do it?
Add safe_reload=True, for config_reload

How did you verify/test it?
Run test_syslog_source_ip on testbed.

Author: ZhaohuiS

tests/syslog/test_syslog_source_ip.py

@@ -97,7 +97,7 @@ def restore_config_by_config_reload(duthosts, enum_rand_one_per_hwsku_frontend_h
                            state='absent', delay=1, timeout=30)
         localhost.wait_for(host=duthost.mgmt_ip, port=SONIC_SSH_PORT, search_regex=SONIC_SSH_REGEX,
                            state='started', delay=2, timeout=180)
-    config_reload(duthost)
+    config_reload(duthost, safe_reload=True)
 
 
 @pytest.fixture(autouse=True)