Do not execute bind on on the LDAP reader thread
Each LDAP connection has a single associated thread, executing the handlers for async requests; this is managed by the LDAP library. The bind operation is blocking for the connection. It is a deadlock to call bind, if on the LDAP reader thread for the same connection, because waiting for the bind response blocks the thread processing responses (for this connection).
This will execute the bind operation (and the subsequent runnable) on a thread pool after checking for the conflict above.
Closes: elastic/x-pack-elasticsearch#2570, elastic/x-pack-elasticsearch#2620
Original commit: elastic/x-pack-elasticsearch@404a3d8737
Albert Zaharovits