all threads are not stopped on Keyspace.close()

[hsn10]

val c = new Cluster(host(0), port).mapHostsEvery(0.seconds)
val keyspace = c.keyspace(repo).connect()
keyspace.close()

running this on "com.twitter" % "cassie-core" % "0.25.2",
results after calling close() in 100% CPU utilisation by some background threads.