Changes

Fix OPCUAConnectorWrapper.invokeMethod()

The method definition was copied incorrectly from the original in
p4m-helpers. The return type of the invokeMethod() method was changed
from List<Object> to Object, which doesn't make sense.
This commit fixes that problem.

I strongly recommend to drop this class entirely and rely instead on
OpcUaClient in p4m-helpers, because that is what it was made for. But
that isn't up to me.

Signed-off-by: Moritz Marseu <moritz.marseu@festo.com>
Change-Id: I6aa8afac0d3c526cb456e7a15321f745e8ea9a22