universe: update pushProofToFederation to make sure all servers are t…

…ried

In this commit, we fix a bug that would cause universe proof push to
fail for all servers, if anyone of them was unreachable, or rejected the
proof.

If we return `err` here, then eventually the context will be read by
other goroutines, which is already cancelled at this point. This'll
cause the push attempt to stop short.

We now long and return `nil` so the other goroutines will continue.

See #527 for more
details.

universe/auto_syncer.go

@@ -257,8 +257,10 @@ func (f *FederationEnvoy) pushProofToFederation(uniID Identifier, key BaseKey,
 	pushNewProof := func(ctx context.Context, addr ServerAddr) error {
 		remoteUniverseServer, err := f.cfg.NewRemoteRegistrar(addr)
 		if err != nil {
-			return fmt.Errorf("unable to connect to remote "+
-				"server(%v): %v", addr.HostStr(), err)
+			log.Warnf("cannot push proof unable to connect "+
+				"to remote server(%v): %v", addr.HostStr(),
+				err)
+			return nil
 		}
 
 		_, err = remoteUniverseServer.RegisterIssuance(