test-commandserver: port test functions from .py to .t
Though we have to duplicate import statements, .t test is still more handy
than .py test which has cryptic .out file.
This change allows to skip a part of test by #if conditional, which my next
patch series depends on.
test-commandserver: add stub for .t test by copying .out with 2-space indent
Currently test-commandserver.t only contains output, so it is skipped by
#require false.