tests: make compatible with autotools

tests: make compatible with autotools

The command 'make check' is called from 'make distcheck' (which is
used to generate official util-linux tarballs).

It means that tests/ stuff has to be compatible with autotools and
differentiate between source and build directories.

 * remove run-nonroot.sh (merged into run.sh
 * remove commands.sh.in
 * all tests and top level run.sh accept --builddir and --srcdir
   command line options
 * functions.sh modified to use $top_builddir/tests for output files

Signed-off-by: Karel Zak <kzak@redhat.com>