fixed a bug that the table metadata lock is not released when open_index is failed

Author: ahiguti

regtest/test_01_lib/test20.expected

@@ -0,0 +1,2 @@
+open_index 1st r=1
+open_index 2nd r=0

regtest/test_01_lib/test20.pl

@@ -0,0 +1,33 @@
+#!/usr/bin/perl
+
+# vim:sw=2:ai
+
+# test for a bug that table mdl is not released when open_index is failed
+
+BEGIN {
+	push @INC, "../common/";
+};
+
+use strict;
+use warnings;
+use hstest;
+
+my $dbh = hstest::init_testdb();
+my $dbname = $hstest::conf{dbname};
+my $table = 'hstesttbl';
+
+$dbh->do("drop table if exists $table");
+
+my $hs = hstest::get_hs_connection();
+my $r = $hs->open_index(1, $dbname, $table, '', 'k,v'); # fails
+print "open_index 1st r=$r\n";
+undef $hs;
+
+$dbh->do(
+  "create table $table (k varchar(30) primary key, v varchar(30) not null) " .
+  "engine = innodb");
+
+$hs = hstest::get_hs_connection();
+$r = $hs->open_index(1, $dbname, $table, '', 'k,v'); # success
+print "open_index 2nd r=$r\n";
+