BUG#27477 Remove tmp-directory on MTR start

mysql-test/mysql-test-run.pl:
  Remove tmp-directory on MTR start

mysql-test/mysql-test-run.pl

@@ -2386,6 +2386,9 @@ sub remove_stale_vardir () {
     mtr_verbose("Removing $opt_vardir/");
     mtr_rmtree("$opt_vardir/");
   }
+  # Remove the "tmp" dir
+  mtr_verbose("Removing $opt_tmpdir/");
+  mtr_rmtree("$opt_tmpdir/");
 }
 
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