spec: Enable fuse only if LXC is enabled

Enabling fuse without LXC does not make a lot of sense because fuse is
used only by LXC.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

libvirt.spec.in

@@ -163,7 +163,7 @@
 %endif
 
 # fuse is used to provide virtualized /proc for LXC
-%if 0%{?fedora} || 0%{?rhel} >= 7
+%if %{with_lxc}
     %define with_fuse      0%{!?_without_fuse:1}
 %endif