[4.4-ubuntu] Fix build under Xenial

Previously I was building this package from under Debian10 and it was
working ok. But trying to build in pristine Xenial environment revealed
that there is not debhelper-compat support at that version. Adjust
control correspondingly (see debian/changelog for details). I've verified
that the resulting built deb is exactly the same as it was before this
change when built on Debian10.

fs/fuse/debian/changelog

+nxd-fuse (4.4.nxd3+ubuntu2) xenial; urgency=medium
+
+  * Switch `Build-Depends: debhelper-compat (= 11)` to `debian/compat = 9`:
+    - on Xenial there is no support for `Build-Depends: debhelper-compat`.
+    - on Xenial the latest supported compatibility level is 9.
+
+ -- Kirill Smelkov <kirr@nexedi.com>  Sun, 11 Oct 2020 12:01:17 +0300
+
 nxd-fuse (4.4.nxd3+ubuntu1) xenial; urgency=medium
 
   * Sync with xenial/master (Ubuntu-4.4.0-190.220).

fs/fuse/debian/compat

+9

fs/fuse/debian/control

@@ -3,8 +3,7 @@ Section: kernel
 Priority: optional
 Maintainer: Kirill Smelkov <kirr@nexedi.com>
 Build-Depends:
-# dh12 uses `invoke-rc.d --skip-systemd-native` that is not supported on Xenial
- debhelper-compat (= 11),
+ debhelper,
  dkms,
 Rules-Requires-Root: no
 Standards-Version: 4.3.0