fix for basic_20: increases timeout for scaling operation

basic_20 is failing due to the timeout value which is 2 mins.
Thanks to David Aguilar we know that this time should be 4 mins.

Change-Id: I683e486b55dea056fb5e6d041ae7e7bd2c97a0d8
Signed-off-by: aktas <emin.aktas@ulakhaberlesme.com.tr>
diff --git a/robot-systest/testsuite/basic_20-manual_native_charm_vdu_scaling.robot b/robot-systest/testsuite/basic_20-manual_native_charm_vdu_scaling.robot
index f270617..6ac3a9b 100644
--- a/robot-systest/testsuite/basic_20-manual_native_charm_vdu_scaling.robot
+++ b/robot-systest/testsuite/basic_20-manual_native_charm_vdu_scaling.robot
@@ -45,6 +45,8 @@
 # Scaling group name of VDU instances
 ${scaling_group}   manual-scaling_mgmtVM
 
+${scale_wait_time}   4min
+
 *** Test Cases ***
 Create VNF Descriptor
 
@@ -105,7 +107,7 @@
 Perform Manual Vdu Scale Out
 
     Variable Should Exist  ${ns_id}  msg=Network service instance is not available
-    ${ns_op_id}=  Execute Manual VNF Scale  ${ns_name}  ${vnf_member_index}  ${scaling_group}  SCALE_OUT
+    ${ns_op_id}=  Execute Manual VNF Scale  ${ns_name}  ${vnf_member_index}  ${scaling_group}  SCALE_OUT  ${scale_wait_time}
 
 
 Check Vdus After Scale Out