tests: shell script portability and clean-up

tests: shell script portability and clean-up

* tests/test-lib.sh: "echo -n" is not portable.  Use printf instead.
Remove unnecessary uses of "eval-in-subshell" (subshell is sufficient).
Remove uses of tests' -a operator; it is not portable.
Instead, use "test cond && test cond2".
* tests/schematestutils.sh: Replace use of test's -a.