3.x: there is some case when driver does not release DefaultResultSetFuture properly

[dkropachev]

It comes from scylladb/cassandra-stress#30.
Time to time it can stuck waiting for DefaultResultSetFuture to be released:

"Thread-2" prio=5 Id=59 WAITING on com.datastax.driver.core.DefaultResultSetFuture@2ad5ebfd
  at [email protected]/jdk.internal.misc.Unsafe.park(Native Method)
  -  waiting on com.datastax.driver.core.DefaultResultSetFuture@2ad5ebfd
  at [email protected]/java.util.concurrent.locks.LockSupport.park(Unknown Source)
  at app//com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:561)
  at app//com.google.common.util.concurrent.Uninterruptibles.getUninterruptibly(Uninterruptibles.java:247)
  at app//com.datastax.driver.core.DefaultResultSetFuture.getUninterruptibly(DefaultResultSetFuture.java:308)
  at app//com.datastax.driver.core.AbstractSession.execute(AbstractSession.java:58)
  at app//org.apache.cassandra.stress.util.JavaDriverClient.executePrepared(JavaDriverClient.java:247)
  at app//org.apache.cassandra.stress.operations.predefined.CqlOperation$JavaDriverWrapper.execute(CqlOperation.java:308)

It means that there is a bug in ReleaseHandler or in DefaultResultSetFuture that leaves DefaultResultSetFuture without set or setException called on it.
As result getUninterruptibly waits for it forever.
to go forward we need to do the following:

1. Check ReleaseHandler and DefaultResultSetFuture to make sure every case ends up in set or setException
2. Find a way for AbstractSession.execute(Statement statement) to have timeout on getUninterruptibly.