Add missing 'return 0;' in stub lxcStartFuse() method impl.

Without a 'return 0' in the stub lxcStartFuse() method, the
compiler warns:

lxc/lxc_fuse.c:374: error: control reaches end of non-void function
[-Wreturn-type]
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/lxc/lxc_fuse.c

@@ -371,6 +371,7 @@ int lxcSetupFuse(virLXCFusePtr *f ATTRIBUTE_UNUSED,
 
 int lxcStartFuse(virLXCFusePtr f ATTRIBUTE_UNUSED)
 {
+    return 0;
 }
 
 void lxcFreeFuse(virLXCFusePtr *f ATTRIBUTE_UNUSED)