fix getReactiveConnection() (opentracing-contrib#43)

RedisConnectionFactory cant castcannot be cask to ReactiveRedisConnection

Author: duoyuli

opentracing-redis-spring-data2/src/main/java/io/opentracing/contrib/redis/spring/data2/connection/TracingRedisConnectionFactory.java

@@ -72,7 +72,7 @@ public DataAccessException translateExceptionIfPossible(RuntimeException e) {
  @Override
  public ReactiveRedisConnection getReactiveConnection() {
  if (delegate instanceof ReactiveRedisConnectionFactory) {
- return new TracingReactiveRedisConnection((ReactiveRedisConnection) delegate,
+ return new TracingReactiveRedisConnection(((ReactiveRedisConnectionFactory) delegate).getReactiveConnection(),
  tracingConfiguration);
  }
  // TODO: shouldn't we throw an exception?