Set system, chassis, and bmc as global variables

Changes:
  - Add SYSTEM_ID as a global variable and set to default value system
  - Replace redfish/v1/Systems/system to redfish/v1/Systems/SYSTEM_ID
  - Replace redfish/v1/Chassis/chassis to redfish/v1/Chassis/CHASSIS_ID
  - Replace redfish/v1/Managers/bmc to redfish/v1/Managers/MANAGER_ID

Tested:
  - Tested on sandbox with the changes with sample test run with
    sample test ID runs
    1. without SYSTEM_ID provided
    2. with -v SYSTEM_ID:system1
    3. with export SYSTEM_ID=""
    3. with export SYSTEM_ID="system2"

Change-Id: Ifc412b20038cef1eba632caaa6c300be328259bd
Signed-off-by: Wilson Suen <wilsons@supermicro.com>
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/openpower/mpipl/test_mpipl_basic.robot b/openpower/mpipl/test_mpipl_basic.robot
index ca1498b..5fd0507 100644
--- a/openpower/mpipl/test_mpipl_basic.robot
+++ b/openpower/mpipl/test_mpipl_basic.robot
@@ -143,7 +143,7 @@
     #       "Name": "System Dump Entry",
     #       "OEMDiagnosticDataType": "System"
     #   }
-    ${sys_dump}=  Redfish.Get Properties  /redfish/v1/Systems/system/LogServices/Dump/Entries
+    ${sys_dump}=  Redfish.Get Properties  /redfish/v1/Systems/${SYSTEM_ID}/LogServices/Dump/Entries
     Log To Console  System dump generated: ${sys_dump['Members@odata.count']}
     Should Be True  ${sys_dump['Members@odata.count']} == 1  msg=No system dump generated.