Skip NVR check if the %autorelease macro is used
If a spec file sets the release field to the %autorelease macro, don't
even attempt to check if the build exists already, as using the macro
ensures that a new release number is used.
Fixes: https://pagure.io/fedora-infra/rpmautospec/issue/109
Signed-off-by: Nils Philippsen <nils@redhat.com>