testdb: pass empty pkglist to alpm_checkdeps

Passing both pkglist and upgrades to alpm_checkdeps does nothing but
cause extra overhead as the packages are all removed from pkglist
because they also exist in upgrades.

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

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

missing perl-test-pod  dependency for perl-test-output

vs

missing 'perl-test-pod ' dependency for 'perl-test-output'

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