[VOL-4355] Fixed hardcoded namespace values

Change-Id: I90894ab10ddcb57d9b59123479240fc9c3c7d967
diff --git a/tests/dt-workflow/Voltha_DT_FailureScenarios.robot b/tests/dt-workflow/Voltha_DT_FailureScenarios.robot
index d9cba37..85055f2 100755
--- a/tests/dt-workflow/Voltha_DT_FailureScenarios.robot
+++ b/tests/dt-workflow/Voltha_DT_FailureScenarios.robot
@@ -42,6 +42,7 @@
 ${HELM_CHARTS_DIR}    ~/helm-charts
 ${VOLTHA_POD_NUM}    8
 ${NAMESPACE}      voltha
+${INFRA_NAMESPACE}      default
 ${STACK_NAME}       voltha
 # For below variable value, using deployment name as using grep for
 # parsing radius pod name, we can also use full radius pod name