Fixing the delete test at scale

Change-Id: Ifbfc4d5a894b7bca2ee27d5ecb95717553940b62
diff --git a/tests/scale/Voltha_Scale_Tests.robot b/tests/scale/Voltha_Scale_Tests.robot
index 33405e1..8a70340 100755
--- a/tests/scale/Voltha_Scale_Tests.robot
+++ b/tests/scale/Voltha_Scale_Tests.robot
@@ -253,10 +253,16 @@
 Disable and Delete devices
     [Documentation]  Disable and delete the OLTs in VOLTHA
     [Tags]      non-critical    teardown
-    FOR    ${olt_device_id}    IN  @{olt_device_ids}
-        Disable Device  ${olt_device_id}
-        Delete Device  ${olt_device_id}
-        Remove Values From List     ${olt_device_ids}   ${olt_device_id}
+
+    ${rc}    ${output}=     Run And Return Rc And Output    voltctl -c ${VOLTCTL_CONFIG} device list -f Type=openolt -q
+    Should Be Equal As Integers    ${rc}    0   Failed to get device list from voltctl: ${output}
+    Log     ${output}
+    ${devices}=     Split To Lines  ${output}
+    Log     ${devices}
+
+    FOR     ${id}   IN  @{devices}
+        Disable Device  ${id}
+        Delete Device  ${id}
     END
 
     ${onos_devices}=    Compute Device IDs
@@ -264,8 +270,6 @@
         Wait for all flows to be removed    ${ONOS_SSH_IP}    ${ONOS_SSH_PORT}  ${deviceId}
     END
 
-    Set Suite Variable    ${olt_device_ids}
-
 *** Keywords ***
 Setup Suite
     [Documentation]    Setup test global variables, open an SSH connection to ONOS and starts a timer