redfish: systems: fix unexpected BMC error logs present issue

Symptom:
Auto test got failed from redfish/systems/test_thermal_ambient_temperatures.robot
Error is "Unexpected BMC error log(s) present.: 200 != 404" and result is FAIL
Get Ambient Temperature Records                         | FAIL |
Reboot And Check Ambient Temperature Records Are Valid  | FAIL |

Root cause:
According keyword "Get Thermal Records and Verify" that will get
the thermal records for temperatures and verify whether there is
any error event log. We found that there are lots of log entries
exist at /xyz/openbmc_project/logging/entry/xxx and test item got failed
in keyword "Error Logs Should Not Exist".

Solution:
Before running thermal ambient temperatures test items, we need to
do "Delete All Error Logs" for clear all event logs first in Test Setup.

Tested:
Run robot test redfish/systems/test_thermal_ambient_temperatures.robot.
Get Ambient Temperature Records                         | PASS |
Reboot And Check Ambient Temperature Records Are Valid  | PASS |

Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: I02003bf1478a26cb716bc6d386d442bf546adf85
diff --git a/redfish/systems/test_thermal_ambient_temperatures.robot b/redfish/systems/test_thermal_ambient_temperatures.robot
index d893145..5837c96 100755
--- a/redfish/systems/test_thermal_ambient_temperatures.robot
+++ b/redfish/systems/test_thermal_ambient_temperatures.robot
@@ -11,7 +11,7 @@
 
 Suite Setup         Suite Setup Execution
 Suite Teardown      Suite Teardown Execution
-Test Setup          Printn
+Test Setup          Delete All Error Logs
 Test Teardown       Test Teardown Execution