Make builds reproducible 

* debian/rules (override_dh_fixperms-arch): Exclude from dh_fixperms
  only what is inside the
  /usr/share/doc/mandos-client/examples/network-hooks.d/ directory.
  That is, do not exclude (i.e. include in the normal dh_fixperms) the
  example/network-hooks.d directory itself.