Add lib keyword to get system power limit

Changes:
    - Added redfish call to get the system power limit

Tested:
    - Currently this code is not use, but wrote a sample test code
      to call this keyword and tested.

Change-Id: I2ddb7dc286f86210912e95a420b194b859de35a2
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/energy_scale_utils.robot b/lib/energy_scale_utils.robot
index d0839bd..9397520 100755
--- a/lib/energy_scale_utils.robot
+++ b/lib/energy_scale_utils.robot
@@ -7,9 +7,28 @@
 Resource          ../lib/ipmi_client.robot
 Library           ../lib/var_funcs.py
 
+*** Variables ***
+
+${power_cap_uri}    /redfish/v1/Chassis/${CHASSIS_ID}/EnvironmentMetrics
 
 *** Keywords ***
 
+Get System Power Cap Limit
+    [Documentation]  Get the allowed MAX and MIN power limit of the chassis.
+
+    # GET request of /redfish/v1/Chassis/chassis/EnvironmentMetrics  | grep -A5 Power
+    #   "PowerLimitWatts": {
+    #       "AllowableMax": 2488,
+    #       "AllowableMin": 1778,
+    #       "ControlMode": "Disabled",
+    #       "SetPoint": 2488
+    # }
+
+    ${power_limit_watts}=  Redfish.Get Attribute  ${power_cap_uri}   PowerLimitWatts
+
+    [return]  ${power_limit_watts}
+
+
 DCMI Power Get Limits
     [Documentation]  Run dcmi power get_limit and return values as a
     ...  dictionary.