Fix for redfishtool certificate, snmp and session management

Changes:
  - Set cert_id as test variable
  - Remove colon in snmp destination when the snmp port is empty
  - Fix redfish_delete_sessions assign location
  - Set REDFISH_DELETE_SESSIONS to 0 in suite setup
  - Set REDFISH_DELETE_SESSIONS back to 1 in suite teardown

Tested:
  - redfish/service_root/test_sessions_management.robot
  - redfish/dmtf_tools/test_redfishtool_certificate.robot
  - redfish/events/test_bmc_snmp_trap.robot

Change-Id: Ibb16d52b5874484f8cf169456e2feb4ba7593e71
Signed-off-by: Wilson Suen <wilsons@supermicro.com>
diff --git a/redfish/service_root/test_sessions_management.robot b/redfish/service_root/test_sessions_management.robot
index 31aa3b4..0bde4f9 100644
--- a/redfish/service_root/test_sessions_management.robot
+++ b/redfish/service_root/test_sessions_management.robot
@@ -18,6 +18,7 @@
 # User-driven input parameter to skip operator user.
 # -v SKIP_OPERATOR_USER:1  to skip from CLI.
 ${SKIP_OPERATOR_USER}    ${0}
+${REDFISH_DELETE_SESSIONS}  ${0}
 
 
 *** Test Cases ***
@@ -293,11 +294,13 @@
 
     Create Users With Different Roles  users=${USERS}  force=${True}
     Get Default Timeout Value
+    Set Redfish Delete Session Flag  ${0}
 
 
 Suite Teardown Execution
     [Documentation]  Suite teardown execution.
 
     Delete BMC Users Via Redfish  users=${USERS}
+    Set Redfish Delete Session Flag  ${1}
     Run Keyword And Ignore Error  Delete All Redfish Sessions
     Redfish.Logout