Use one err file for each master

mysql-test/mysql-test-run.sh:
  Add master id to end of MASTER_MY_ERR  so that both masters doesnt write to the same file.

mysql-test/mysql-test-run.sh

@@ -1181,8 +1181,8 @@ start_master()
            $NOT_FIRST_MASTER_EXTRA_OPTS"
   fi
 
-  CUR_MYERR=$MASTER_MYERR
-  CUR_MYSOCK=$MASTER_MYSOCK
+  CUR_MYERR=$MASTER_MYERR$1
+  CUR_MYSOCK=$MASTER_MYSOCK$1
 
   # For embedded server we collect the server flags and return
   if [ "x$USE_EMBEDDED_SERVER" = "x1" ] ; then