extra/runner/run: Fix infinite loop
extra/runner/run: Fix infinite loop

The previous commit (233889de) ran the `while` loop from a sub-process,
because of the `parse_test_args | while` pipeline. Inside this
sub-process, any `break` statement couldn't affect the parent process,
so it couldn't break out of the outermost `while true` loop. Similarly,
any `exit` called from `run` would stop the current iteration, but it
wouldn't exit the parent process, so another iteration would run.

By moving the `parse_test_args` call outside of a pipeline, the `while
read ...` loop is run in the main process. `while` and `read` are both
bash builtins.

stb-tester/stb-tester,wmanley/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester