Update peer validation (#1838)

* Update peer validation

Change the location where peer validation is checked for height
estimates.  Too early and all of peer discovery is stopped.

Signed-off-by: Danno Ferrin <danno.ferrin@gmail.com>

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/manager/EthPeer.java

@@ -331,9 +331,7 @@ public class EthPeer {
    * @return true if the peer is ready to accept requests for data.
    */
   public boolean readyForRequests() {
-    return statusHasBeenSentToPeer.get()
-        && statusHasBeenReceivedFromPeer.get()
-        && fullyValidated.get();
+    return statusHasBeenSentToPeer.get() && statusHasBeenReceivedFromPeer.get();
   }
 
   /**

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/manager/EthPeers.java

@@ -153,7 +153,8 @@ public class EthPeers {
   }
 
   public Optional<EthPeer> bestPeerWithHeightEstimate() {
-    return bestPeerMatchingCriteria(p -> p.chainState().hasEstimatedHeight());
+    return bestPeerMatchingCriteria(
+        p -> p.isFullyValidated() && p.chainState().hasEstimatedHeight());
   }
 
   public Optional<EthPeer> bestPeerMatchingCriteria(final Predicate<EthPeer> matchesCriteria) {