don't need to tag the slave SQL thread as "bootstrap". It causes duplicate

error messages when a query goes wrong.
Note that from now on, if you run with --slave-skip-error=xx, then nothing will
be printed to the error log when the slave is having this error xx and
skipping it (but you don't care as you want to skip it).

sql/repl_failsafe.cc

@@ -63,6 +63,11 @@ static Slave_log_event* find_slave_event(IO_CACHE* log,
 static int init_failsafe_rpl_thread(THD* thd)
 {
   DBUG_ENTER("init_failsafe_rpl_thread");
+  /*
+    thd->bootstrap is to report errors barely to stderr; if this code is
+    enable again one day, one should check if bootstrap is still needed (maybe
+    this thread has no other error reporting method).
+  */
   thd->system_thread = thd->bootstrap = 1;
   thd->host_or_ip= "";
   thd->client_capabilities = 0;

sql/slave.cc

@@ -2516,7 +2516,6 @@ static int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type)
   DBUG_ENTER("init_slave_thread");
   thd->system_thread = (thd_type == SLAVE_THD_SQL) ?
     SYSTEM_THREAD_SLAVE_SQL : SYSTEM_THREAD_SLAVE_IO; 
-  thd->bootstrap= 1;
   thd->host_or_ip= "";
   thd->client_capabilities = 0;
   my_net_init(&thd->net, 0);