Primary server support: support for "disconnecting" connections in LDAP
    
    This patch adds support for marking existing connections as being
    disconnected. Each such connection can't be used for new queries and a
    new one has to be created instead if necessary. This will ensure that
    pending operations will end gracefully during reconnection. Also all new
    queries to the server we are reconnecting to will use another (probably
    newly created) connection.