BUG#12929631 : Execute crashes with --verbose output (Windows)

This patch corrects an error encountered in PB where Windows machines
are built in release mode have an extraneous parameter added in place
of the --console option. This is caused by the insert of '(null' 
instead of an empty string. In non-debug mode, the string is explicitly
set to an empty string.

Patch also fixes a result mismatch on Windows machines.

client/mysql_plugin.c

@@ -1169,6 +1169,8 @@ static int bootstrap_server(char *server_path, char *bootstrap_file)
   
   if (opt_verbose)
     verbose_str= "--console";
+  else
+    verbose_str= "";
   if (has_spaces(opt_datadir) || has_spaces(opt_basedir) ||
       has_spaces(bootstrap_file))
     format_str= "\"%s %s --bootstrap --datadir=%s --basedir=%s < %s\"";

mysql-test/t/mysql_plugin.test

@@ -224,6 +224,7 @@ let $MYSQL_PLUGIN_CMD= $MYSQL_PLUGIN -n --datadir=/data_not_there/ --basedir=$MY
 --echo # Attempt to use bad paths - basedir
 --echo #
 let $MYSQL_PLUGIN_CMD= $MYSQL_PLUGIN -n --datadir=$MYSQLD_DATADIR --basedir=/basedir_not_there/ --plugin-dir=$PLUGIN_DIR --mysqld=$MYSQLD_BASEDIR --my-print-defaults=$MYSQL_MY_PRINT_DEFAULTS_BASEDIR;
+replace_result "/basedir_not_there//" "/basedir_not_there/";
 --error 1,2,256
 --exec $MYSQL_PLUGIN_CMD DISABLE daemon_example 2>&1