Add more unittests for ignored problem error paths

Related to rhbz#909968 and rhbz#905412

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Add maintainer-check-valgrind make target

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Fix leaks in koops-parser unit tests

Signed-off-by: Jakub Filak <jfilak@redhat.com>