testdb: quote output substitutions

Quoting output substitutions makes whitespace errors such as FS#30101
much more obvious:

old:
    missing perl-test-pod  dependency for perl-test-output
new:
    missing 'perl-test-pod ' dependency for 'perl-test-output'

Several of the quoted substitutions should not be capable of containing
whitespace in theory, but this errs on the side of caution as the point
of the tool is to find errors.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>