Revise how test suite is run.

Fixing the test suite for my recent refactorings ended up being quite
the trip through the looking glass.

I ended up making the run-test phase not enabled by default due to
always filtering it out in the test suite. So naturally I just add it
back in if we're using the run-tests option. But naturally *that* change
warrants test suite coverage, and testing it out gave me error about
finding main::list_has, since list_has is really test::list_has when the
test suite is being run.

Using Perl's caller function allows me to reset the package to main at
the start of kdesrc-build and still detect when it's being activated as
part of the test suite, but then the functions in the test suite don't
work until I switch *its* package to match.

It all does seem to work now though.