Fix OPENDJ-1247: Client side timeouts do not cancel bind or startTLS requests properly

* fail the connection when a bind or startTLS request times out
* ensure that abandon requests are sent for other types of operation
* fix a bug which meant that the timeout checker could fail to enforce timeouts for the first LDAP connection
* minor improvements: only register connections which have a non-zero timeout; remove duplicate requestID field from LDAP future implementation
* added unit tests. These tests are a bit too functional at the moment and will be split up in a subsequent change.