demote libnss-mdns to suggests

At recommends it causes avahi-daemon to be pulled in on upgrade, which is
just too annoying to deal with avoiding on servers. MDNS is needed for
robust peering, but probably most desktop systems have it anyway; it's in
task-desktop.

debian/control

@@ -59,8 +59,8 @@ Depends: ${misc:Depends}, ${shlibs:Depends},
 	rsync,
 	wget | curl,
 	openssh-client (>= 1:5.6p1)
-Recommends: lsof, libnss-mdns, gnupg
-Suggests: graphviz, bup
+Recommends: lsof, gnupg
+Suggests: graphviz, bup, libnss-mdns
 Description: manage files with git, without checking their contents into git
  git-annex allows managing files with git, without checking the file
  contents into git. While that may seem paradoxical, it is useful when