Addendum to the fix for bug #11754014

- Fixed the checks to properly check for plugin_dir containing a trailing slash or backslash.
- Fixed a under-configuration in udf_skip_grants that was preventing the test 
  from running even when there was a udf plugin.

mysql-test/include/have_example_plugin.inc

@@ -15,7 +15,7 @@ if (!$EXAMPLE_PLUGIN) {
 #
 # Check if --plugin-dir was setup for exampledb
 #
-if (`SELECT CONCAT('--plugin-dir=', @@plugin_dir) != '$EXAMPLE_PLUGIN_OPT'`) {
+if (`SELECT CONCAT('--plugin-dir=', REPLACE(@@plugin_dir, '\\\\', '/')) != '$EXAMPLE_PLUGIN_OPT/'`) {
   --skip Example plugin requires that --plugin-dir is set to the example plugin dir (either the .opt file does not contain \$EXAMPLE_PLUGIN_OPT or another plugin is in use)
 }
 enable_query_log;

mysql-test/include/have_semisync_plugin.inc

@@ -16,6 +16,6 @@ if (!$SEMISYNC_MASTER_PLUGIN)
 #
 # Check if --plugin-dir was setup for semisync
 #
-if (`SELECT CONCAT('--plugin-dir=', @@plugin_dir) != '$SEMISYNC_PLUGIN_OPT'`) {
+if (`SELECT CONCAT('--plugin-dir=', REPLACE(@@plugin_dir, '\\\\', '/')) != '$SEMISYNC_PLUGIN_OPT/'`) {
   --skip SEMISYNC plugin requires that --plugin-dir is set to the semisync plugin dir (either the .opt file does not contain \$SEMISYNC_PLUGIN_OPT or another plugin is in use)
 }

mysql-test/include/have_simple_parser.inc

@@ -15,6 +15,6 @@ if (!$SIMPLE_PARSER) {
 #
 # Check if --plugin-dir was setup for simple parser
 #
-if (`SELECT CONCAT('--plugin-dir=', @@plugin_dir) != '$SIMPLE_PARSER_OPT'`) {
+if (`SELECT CONCAT('--plugin-dir=', REPLACE(@@plugin_dir, '\\\\', '/')) != '$SIMPLE_PARSER_OPT/'`) {
   --skip simple parser requires that --plugin-dir is set to the udf plugin dir (either the .opt file does not contain \$UDF_EXAMPLE_LIB_OPT or another plugin is in use)
 }

mysql-test/include/have_udf.inc

@@ -15,6 +15,6 @@ if (!$UDF_EXAMPLE_LIB) {
 #
 # Check if --plugin-dir was setup for udf
 #
-if (`SELECT CONCAT('--plugin-dir=', @@plugin_dir) != '$UDF_EXAMPLE_LIB_OPT'`) {
+if (`SELECT CONCAT('--plugin-dir=', REPLACE(@@plugin_dir, '\\\\', '/')) != '$UDF_EXAMPLE_LIB_OPT/'`) {
   --skip UDF requires that --plugin-dir is set to the udf plugin dir (either the .opt file does not contain \$UDF_EXAMPLE_LIB_OPT or another plugin is in use)
 }

mysql-test/t/udf_skip_grants-master.opt

 --skip-grant-tables
+$UDF_EXAMPLE_LIB_OPT