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/lib/dump_utils.robot b/lib/dump_utils.robot
index d320059..02b203c 100644
--- a/lib/dump_utils.robot
+++ b/lib/dump_utils.robot
@@ -194,7 +194,7 @@
 Redfish Delete All System Dumps
     [Documentation]  Delete all system  dumps via Redfish.
 
-    Redfish.Post  /redfish/v1/Systems/system/LogServices/Dump/Actions/LogService.ClearLog
+    Redfish.Post  /redfish/v1/Systems/${SYSTEM_ID}/LogServices/Dump/Actions/LogService.ClearLog
 
 
 Redfish BMC Dump Should Not Exist