Fix to be sure subscriber is ready when subscription is used (Consensys#8209)

Author: zilm13

Diff for: services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainController.java

@@ -890,12 +890,12 @@ public void initValidatorApiHandler() {
         new GraffitiBuilder(
             beaconConfig.validatorConfig().getClientGraffitiAppendFormat(),
             beaconConfig.validatorConfig().getGraffitiProvider().get());
+    eventChannels.subscribe(ExecutionClientVersionChannel.class, graffitiBuilder);
     final ExecutionClientVersionProvider executionClientVersionProvider =
         new ExecutionClientVersionProvider(
             executionLayer,
             eventChannels.getPublisher(ExecutionClientVersionChannel.class),
             graffitiBuilder.getConsensusClientVersion());
-    eventChannels.subscribe(ExecutionClientVersionChannel.class, graffitiBuilder);
     final BlockOperationSelectorFactory operationSelector =
         new BlockOperationSelectorFactory(
             spec,