Backporting a patch for Bug#49170 (Inconsistent placement of semisync

plugin prevents it from getting tested) from mysql-next-mr-bugfixing
to mysql-trunk-bugfixing.

Original revision:
------------------------------------------------------------
revision-id: zhenxing.he@sun.com-20091204014339-2m06r42vajhm9vke
committer: He Zhenxing <zhenxing.he@sun.com>
branch nick: 5.1-rep-semisync
timestamp: Fri 2009-12-04 09:43:39 +0800
message:
  Bug#49170 Inconsistent placement of semisync plugin prevents it from getting tested
  
  Add $basedir/lib/plugin to the search paths for semisync plugins.
------------------------------------------------------------

mysql-test/mysql-test-run.pl

@@ -1849,11 +1849,13 @@ sub environment_setup {
     my $lib_semisync_master_plugin=
       mtr_file_exists(vs_config_dirs('plugin/semisync',$semisync_master_filename),
 		      "$basedir/plugin/semisync/.libs/" . $semisync_master_filename,
-                      "$basedir/lib/mysql/plugin/" . $semisync_master_filename);
+                      "$basedir/lib/mysql/plugin/" . $semisync_master_filename,
+                      "$basedir/lib/plugin/" . $semisync_master_filename);
     my $lib_semisync_slave_plugin=
       mtr_file_exists(vs_config_dirs('plugin/semisync',$semisync_slave_filename),
 		      "$basedir/plugin/semisync/.libs/" . $semisync_slave_filename,
-                      "$basedir/lib/mysql/plugin/" . $semisync_slave_filename);
+                      "$basedir/lib/mysql/plugin/" . $semisync_slave_filename,
+                      "$basedir/lib/plugin/" . $semisync_slave_filename);
     if ($lib_semisync_master_plugin && $lib_semisync_slave_plugin)
     {
       $ENV{'SEMISYNC_MASTER_PLUGIN'}= basename($lib_semisync_master_plugin);