SPY-140: Use LinkedBlockingQueue for listener task queuing.

Change-Id: I3e3db7861a6e6e6c24c61c40ea02b19c8bc57fab
Reviewed-on: http://review.couchbase.org/29548
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>