HTTPError 500 POST on Session raises an exception

To handle 500 Server Error: Internal Server Error for URL
when the test suite is executed for the error scenario.

Changes:
     - Added expect_status to handle error response.
       Without this, it raises exceptions and fails.

Tested:
    Ran test suite
	redfish/dmtf_tools/test_redfishtool_certificate.robot

Change-Id: I423438ca2d0de286e658bc196a3746dcc057e11b
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/dmtf_tools/test_redfishtool_certificate.robot b/redfish/dmtf_tools/test_redfishtool_certificate.robot
index 63d0280..b3a6794 100644
--- a/redfish/dmtf_tools/test_redfishtool_certificate.robot
+++ b/redfish/dmtf_tools/test_redfishtool_certificate.robot
@@ -334,7 +334,7 @@
     ...  X-Auth-Token=${XAUTH_TOKEN}
     Set To Dictionary  ${kwargs}  headers  ${headers}
 
-    ${resp}=  POST On Session  openbmc  ${uri}  &{kwargs}
+    ${resp}=  POST On Session  openbmc  ${uri}  &{kwargs}  expected_status=any
     ${cert_id}=  Set Variable If  '${resp.status_code}' == '${HTTP_OK}'  ${resp.json()["Id"]}  -1
 
     Run Keyword If  '${status}' == 'ok'