Managers ID : Introduced variable to declare Managers ID in resource.robot and updated all the scripts in openbmc-test-automation

Changes:
    - Introduced ${MANAGER_ID} variable in resource.robot
    - Replaced all the Managers/bmc to Managers/${MANAGER_ID} across all the scripts
    - Also in data/variables.py updated chassis id for the few redfish uri.

Tested:
     - Ran All The Scripts Successfully

Change-Id: Iff3673aae27657e0799dec5cb94c1651a0cd5d18
Signed-off-by: ganesanb <ganesanb@ami.com>
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/service_root/test_service_root.robot b/redfish/service_root/test_service_root.robot
index a360c3f..3c33c69 100644
--- a/redfish/service_root/test_service_root.robot
+++ b/redfish/service_root/test_service_root.robot
@@ -49,7 +49,7 @@
     ${HTTP_OK}           /redfish/v1/AccountService
     ${HTTP_OK}           /redfish/v1/Systems/system
     ${HTTP_OK}           /redfish/v1/Chassis/${CHASSIS_ID}
-    ${HTTP_OK}           /redfish/v1/Managers/bmc
+    ${HTTP_OK}           /redfish/v1/Managers/${MANAGER_ID}
     ${HTTP_OK}           /redfish/v1/UpdateService