Call addIsConnected when building NTMultiChannel

isConnected is not a required field of NTMultiChannel, so an instance of
NTMultiChannel wrapper class in normativeTypesCPP built by the builder
does not have this by default and addIsConnected must be called to
provide this field.

src/pvaClientNTMultiData.cpp

@@ -57,7 +57,7 @@ PvaClientNTMultiData::PvaClientNTMultiData(
          unionValue[i] = pvDataCreate->createPVUnion(u);
     }
     NTMultiChannelBuilderPtr builder = NTMultiChannel::createBuilder();
-    builder->value(u);
+    builder->value(u)->addIsConnected();
     if(pvRequest->getSubField("field.alarm"))
     {
          gotAlarm = true;