BUG: fix failing test

Fix the write CLI test for the markpus node by adjusting the expected number
of arguments to be 2 times the number of points, as the flag is written
separately now.

Related to fixes for issue #1910


git-svn-id: http://svn.slicer.org/Slicer4/trunk@22399 3bd1e089-480b-0410-8dfb-8563597acbee