Add Atomic Value's getAndSet() to stc test

- Part of [ONOS-2451]

Change-Id: Ic428f2aa56c5bafdf44cd9951504e5ba1d92bf2b
diff --git a/tools/test/scenarios/dist-value.xml b/tools/test/scenarios/dist-value.xml
index f371d91..cda15cd 100644
--- a/tools/test/scenarios/dist-value.xml
+++ b/tools/test/scenarios/dist-value.xml
@@ -45,8 +45,16 @@
               requires="Distributed-Primitive-Value.Test-Value-CompareAndSet-True"
               exec="onos-cluster-execute-expect value-test test-value get --expect v1"/>
 
-        <step name="Distributed-Primitive-Value.Destroy-Value"
+        <step name="Distributed-Primitive-Value.Test-Value-GetAndSet"
               requires="Distributed-Primitive-Value.Test-Value-Updated-After-CAS"
+              exec="onos-execute-expect ${OCI} value-test test-value getAndSet v2 --expect v1"/>
+
+        <step name="Distributed-Primitive-Value.Test-Value-Updated-After-GetAndSet"
+              requires="Distributed-Primitive-Value.Test-Value-GetAndSet"
+              exec="onos-cluster-execute-expect value-test test-value get --expect v2"/>
+
+        <step name="Distributed-Primitive-Value.Destroy-Value"
+              requires="Distributed-Primitive-Value.Test-Value-Updated-After-GetAndSet"
               exec="onos ${OCI} value-test test-value set null"/>
 
         <group name="Distributed-Primitive-Value.Check-Log-Exceptions"