Merge branch 'clean_up_test_scripts' of https://github.com/cgoesche/util-linux-fork

* 'clean_up_test_scripts' of https://github.com/cgoesche/util-linux-fork:
  tests: do not mix string and array
  tests: use bash parameter substitution instead of echo & sed
  tests: remove unneeded $ in arithmetic expressions
  tests: use find instead of ls for more robust processing
  tests: directly check exitcode for stability and code simplicity
  tests: (lib) avoid repetitive file openings with identical redirects
  tests: quote TS_{OUTPUT,ERRLOG} variables