Add more explicit console logging + minor fixes

* The checks with keywords such as "Should Not Be Empty", "Should
  Be Equal As"... should have a more explicit message on fail, so that
  the console output shows a clearer failing reason.
* Other minor fixes included in the commit are:
	* The Sadis file comparison to None string.
	* The KUBECTL_CONFIG variable not properly set, altough
	  apparently unused.

Change-Id: I9305ba791dd43c9088a7bcbcc9af568ae127f60f
diff --git a/tests/openonu-go-adapter/Voltha_ONUFlowChecks.robot b/tests/openonu-go-adapter/Voltha_ONUFlowChecks.robot
index 1947f52..197efde 100755
--- a/tests/openonu-go-adapter/Voltha_ONUFlowChecks.robot
+++ b/tests/openonu-go-adapter/Voltha_ONUFlowChecks.robot
@@ -156,8 +156,8 @@
     ${result}=    Prepare ONU Go Adapter ETCD Data For Json    ${etcddata}
     ${jsondata}=    To Json    ${result}
     ${length}=    Get Length    ${jsondata}
-    log    ${jsondata}
-    Should Not Be Empty     ${jsondata}
+    Log    ${jsondata}
+    Should Not Be Empty     ${jsondata}     Could not find ONU Go Adapter ETCD data
     FOR    ${INDEX}    IN RANGE    0    ${length}
         ${value}=    Get From List    ${jsondata}    ${INDEX}
         ${flowparams}=    Get From Dictionary    ${value['uni_config'][0]}    flow_params
@@ -199,7 +199,7 @@
     ${jsondata}=    To Json    ${result}
     ${length}=    Get Length    ${jsondata}
     log    ${jsondata}
-    Should Not Be Empty     ${jsondata}
+    Should Not Be Empty     ${jsondata}     Could not find ONU Go Adapter ETCD data
     FOR    ${INDEX}    IN RANGE    0    ${length}
         ${value}=    Get From List    ${jsondata}    ${INDEX}
         @{result_values}=    Run Keyword And Ignore Error