contrib/rpm: explicitly set runstatedir to "/run" when building release tarball

Nowadays, we should prefer "/run" over "/var/run". When not specifying
during ./configure, autotools however still defaults to "/var/run".

This default is also visible in the pre-generated documenation, for
example `man NetworkManager.conf` says

  Unless the symlink points to the internal file /run/NetworkManager/resolv.conf,
  in which case the ...

contrib/fedora/rpm/build_clean.sh

@@ -130,6 +130,7 @@ fi
 
 if [[ $NO_DIST != 1 ]]; then
     ./autogen.sh \
+        --with-runstatedir=/run \
         --program-prefix= \
         --prefix=/usr \
         --exec-prefix=/usr \