Show empty TabularData MBean operation results

When showing the results of an MBean operation, we do not handle TabularData return values of size 0. What is shown is the toString representation of the TabularData object.

I would instead like to see a "TabularData, size 0" string which is what we show in the attributes tab.

TabularData return values with size >= 1 are shown as expected.

Example of how the toString representation looks:
javax.management.openmbean.TabularDataSupport(tabularType=javax.management.openmbean.TabularType(name=java.util.Map<java.lang.String, java.lang.String>,rowType=javax.management.openmbean.CompositeType(name=java.util.Map<java.lang.String, java.lang.String>,items=((itemName=key,itemType=javax.management.openmbean.SimpleType(name=java.lang.String)),(itemName=value,itemType=javax.management.openmbean.SimpleType(name=java.lang.String)))),indexNames=(key)),contents={})