@Override
  public Object execute(Op op) {
    // if(multiuser)
    // get a server from threadlocal cache else throw cacheWriterException
    // executeOn(ServerLocation server, Op op, boolean accessed,boolean onlyUseExistingCnx)

    // Retries are ignored here. FIX IT - FIXED.
    // But this may lead to a user getting authenticated on all servers, even if
    // a single server could have serviced all its requests.
    authenticateIfRequired(null, op);
    return executor.execute(op);
  }
Execute the given op on the servers that this pool connects to. This method is responsible for
retrying the op if an attempt fails. It will only execute it once and on one server.

@param op the operation to execute
@return the result of execution if any; null if not
@since GemFire 5.7
geode-core/src/main/java/org/apache/geode/cache/client/internal/PoolImpl.java