packaging: disable postinst auto-setup

Disabled keys generation because it could lead to change of certificate
during an update => security issue.
Reconfiguration of yaml is disabled because user will now have to run
`dhtnet-crtmgr --interactive`, which create the file if needed.

Change-Id: I388ab1cebf75d248600f070be4eb108766bfe993
diff --git a/extras/packaging/gnu-linux/debian/rules b/extras/packaging/gnu-linux/debian/rules
index bb4a235..fc2266f 100755
--- a/extras/packaging/gnu-linux/debian/rules
+++ b/extras/packaging/gnu-linux/debian/rules
@@ -16,3 +16,4 @@
 	      -DCMAKE_LIBRARY_ARCHITECTURE="$(DEB_TARGET_MULTIARCH)" \
 		  -DBUILD_TESTING=OFF
 		  -DBUILD_BENCHMARKS=OFF
+		  -DDNC_SYSTEMD=ON