Memory Leak: Database reference held by a ReplicatorListenerThread after close

Hello,

Using: CB 2.1.0
I inspect my app memory after stop my two replicators and closing and releasing my Database.

I observed that the both replicators are keep by a ReplicatorListenerThread and by the same way the Database reference's is keep too.

Note:
All references at any couchbase Documents or Database are release by my app.
I force Garbage Collecte to release memory.
The database was closed after both Replication has stopped properly.

This is memory leak or normal behavior ?