WIP still broken...

one problem is that the missing features test happens very early!
if we get wants from :want_foo then those have already been processed

but if we get wants from ordinary magic (e.g. :Replication), that
magic doesn't get invoked until _create_instances() is run, and at
that point it's too late to start adding stuff to the needs hash,
the skip_missing_features filter has already run!

can we _run_magic() earlier, perhaps?

the alternative is needing to add a bunch of :want_replica and such
to tests that previously implicitly got that by having "replication"
in their name or ":Replication" in their attributes.

cassandane/Cassandane/Cyrus/TestCase.pm

@@ -238,6 +238,7 @@ sub want
 
     if ($want_needs->{$name}) {
         foreach my $need (@{$want_needs->{$name}}) {
+            xlog "XXX want '$name' implies need @{$need}";
             $self->needs(@{$need});
         }
     }

cassandane/tiny-tests/Caldav/replication_delete

@@ -2,7 +2,7 @@
 use Cassandane::Tiny;
 
 sub test_replication_delete
-    :needs_component_replication
+    :want_replica
 {
     my ($self) = @_;