Use ATTR_LB_ADDRS from GrpclbConstants instead of GrpcAttributes.

Author: voidzcy

grpclb/src/main/java/io/grpc/grpclb/GrpclbLoadBalancer.java

@@ -92,7 +92,7 @@ public void handleSubchannelState(Subchannel subchannel, ConnectivityStateInfo n
  @SuppressWarnings("deprecation") // TODO(creamsoup) migrate to use parsed service config
  public void handleResolvedAddresses(ResolvedAddresses resolvedAddresses) {
  Attributes attributes = resolvedAddresses.getAttributes();
- List<EquivalentAddressGroup> newLbAddresses = attributes.get(GrpcAttributes.ATTR_LB_ADDRS);
+ List<EquivalentAddressGroup> newLbAddresses = attributes.get(GrpclbConstants.ATTR_LB_ADDRS);
  if ((newLbAddresses == null || newLbAddresses.isEmpty())
  && resolvedAddresses.getAddresses().isEmpty()) {
  handleNameResolutionError(