Move the check for socket path truncation to after the tmpdir has been created

since it's used by the check

mysql-test/mysql-test-run.pl

@@ -606,15 +606,6 @@ sub command_line_setup {
   $opt_tmpdir=       "$opt_vardir/tmp" unless $opt_tmpdir;
   $opt_tmpdir =~ s,/+$,,;       # Remove ending slash if any
 
-  # On some operating systems, there is a limit to the length of a
-  # UNIX domain socket's path far below PATH_MAX.
-  # Don't allow that to happen
-  if (check_socket_path_length("$opt_tmpdir/testsocket.sock")){
-    mtr_error("Socket path '$opt_tmpdir' too long, it would be ",
-	      "truncated and thus not possible to use for connection to ",
-	      "MySQL Server. Set a shorter with --tmpdir=<path> option");
-  }
-
   # --------------------------------------------------------------------------
   # fast option
   # --------------------------------------------------------------------------
@@ -1440,6 +1431,15 @@ sub setup_vardir() {
     symlink($opt_tmpdir, "$opt_vardir/tmp");
   }
 
+  # On some operating systems, there is a limit to the length of a
+  # UNIX domain socket's path far below PATH_MAX.
+  # Don't allow that to happen
+  if (check_socket_path_length("$opt_tmpdir/testsocket.sock")){
+    mtr_error("Socket path '$opt_tmpdir' too long, it would be ",
+	      "truncated and thus not possible to use for connection to ",
+	      "MySQL Server. Set a shorter with --tmpdir=<path> option");
+  }
+
   # copy all files from std_data into var/std_data
   # and make them writable
   copytree("$glob_mysql_test_dir/std_data", "$opt_vardir/std_data");