18437 - mco plugin doc broken for data plugins

In the past mco plugin doc failed when passing a data agent as the
parameter.

In this commit mco plugin doc will correctly display the meta and help
data for a data plugin.
18437 - mco plugin doc broken for data plugins

Update changelog
18466 - Data::Result#method_missing raises incorrect exception

When calling a method on a class that does not exist ruby expects a
NoMethodError to be raised.

The Result::Data class has a method_missing that allows access to data
items via faked methods and it checks for unknown data items and raises
an error but unfortunately it raised the wrong exception type.

We now raise NoMethodError as expected