Two bug fixes related to mirroring:

- default_hostgroup was not set: this causes multiplexing to always be disabled
- fd in client_myds for mirror session was not initialized: this causes random crashes

lib/MySQL_Session.cpp

@@ -783,6 +783,7 @@ __get_pkts_from_client:
 											newsess->client_myds = new MySQL_Data_Stream();
 											newsess->client_myds->DSS=STATE_SLEEP;
 											newsess->client_myds->sess=newsess;
+											newsess->client_myds->fd=0;
 											newsess->client_myds->myds_type=MYDS_FRONTEND;
 											newsess->client_myds->PSarrayOUT= new PtrSizeArray();
 											newsess->thread_session_id=__sync_fetch_and_add(&glovars.thread_id,1);
@@ -793,6 +794,7 @@ __get_pkts_from_client:
 											newsess->client_myds->attach_connection(myconn);
 											newsess->client_myds->myprot.init(&newsess->client_myds, newsess->client_myds->myconn->userinfo, newsess);
 											newsess->to_process=1;
+											newsess->default_hostgroup=default_hostgroup;
 											if (qpo->mirror_hostgroup>= 0) {
 												newsess->mirror_hostgroup=qpo->mirror_hostgroup; // in the new session we copy the mirror hostgroup
 											} else {