warning/bug? in dataman

Created by: germasch

I'm getting this warning in DataManWriter:

[13/86] Building CXX object source/adios2/CMakeFiles/adios2.dir/engine/dataman/DataManWriter.cpp.o
../source/adios2/engine/dataman/DataManWriter.cpp:157:29: warning: comparison of unsigned expression >= 0 is always true [-Wtautological-compare]
        if (request->size() >= 0)
            ~~~~~~~~~~~~~~~ ^  ~
1 warning generated.

I don't know the correct fix is, though. Since the request size is never negative, the current behavior is to always send a reply, even if the request size is 0. If that's the intended behavior, the if statement should just be removed. If the intention was to only reply to messages with a size strictly greater than 0, well, then there's an actual bug.