tmf: Fix remote test failing on Windows

tmf: Fix remote test failing on Windows

IFileInfo.getSize() returns 0 for directories on Windows. "For
directories, the return value is unspecified" so the right thing to do
is to add an isDirectory check.

Change-Id: I6112287adc6cef8fcd7c609edab5bbdfbd933ba3
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/60756
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>