lintian: Use optional priority

Change-Id: Ib397687866b47acf1cbbc6f77bf604b560a2cd2f
(cherry picked from commit 77620b41e6ddea9569ac2be9d35447761974db46)
1 file changed
tree: 902c4811c281f31a229158b1bd9a923ccb60f547
  1. debian/