Bug#47801 The plugin test fails with the Embedded Server on Windows

- Remove the "hack" from mtr.pl that skipped searching for the .dll files
  when embedded and windows. Now the variables will be preoperly initialized.
 - Make the tests detect that they can't run on windows+embedded

mysql-test/include/not_windows_embedded.inc

@@ -0,0 +1,11 @@
+let $is_win = `select convert(@@version_compile_os using latin1) IN ("Win32","Win64","Windows")`;
+let $is_embedded = `select version() like '%embedded%'`;
+#echo is_win: $is_win;
+#echo is_embedded: $is_embedded;
+if ($is_win)
+{
+  if ($is_embedded)
+  {
+    skip Not supported with embedded on windows;
+  }
+}

mysql-test/mysql-test-run.pl

@@ -1797,7 +1797,7 @@ sub environment_setup {
   # --------------------------------------------------------------------------
   # Add the path where mysqld will find ha_example.so
   # --------------------------------------------------------------------------
-  if ($mysql_version_id >= 50100 && !(IS_WINDOWS && $opt_embedded_server)) {
+  if ($mysql_version_id >= 50100) {
     my $plugin_filename;
     if (IS_WINDOWS)
     {

mysql-test/t/plugin.test

@@ -1,3 +1,4 @@
+--source include/not_windows_embedded.inc
 --source include/have_example_plugin.inc
 
 CREATE TABLE t1(a int) ENGINE=EXAMPLE;

mysql-test/t/plugin_load.test

@@ -1,3 +1,4 @@
+--source include/not_windows_embedded.inc
 --source include/have_example_plugin.inc
 
 SELECT @@global.example_enum_var = 'e2';