Add the sources_location argument to SpecFile as we need it

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Fix tests due to added sources_location

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Remove test for _update_filtered_spec_content

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