Remove unused spec_filtered_content variable

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Rework get_sources() and get_patches()

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Remove unneeded _get_full_source_name()

Signed-off-by: Tomas Hozza <thozza@redhat.com>