Remove assignments of the $MASTER_MYSOCK variable.

This variable is defined by default and one should not do it
directly as the socket variable is not available on Windows.

mysql-test/suite/funcs_1/datadict/is_key_column_usage.inc

@@ -126,7 +126,6 @@ ORDER BY constraint_catalog, constraint_schema, constraint_name,
 eval $select;
 
 --echo # Establish connection testuser1 (user=testuser1)
-let $MASTER_MYSOCK= query_get_value(SHOW VARIABLES LIKE 'socket', Value, 1);
 --replace_result $MASTER_MYPORT MYSQL_PORT $MASTER_MYSOCK MYSQL_SOCK
 connect (testuser1, localhost, testuser1, , db_datadict);
 eval $select;