Move the check that $opt_vardir could be created and was writable to the function

where we know how to creat the vardir 
Remove unused variable

mysql-test/mysql-test-run.pl

@@ -1883,7 +1883,6 @@ sub kill_running_servers () {
    }
 }
 
-
 #
 # Remove var and any directories in var/ created by previous
 # tests
@@ -1935,7 +1934,6 @@ sub remove_stale_vardir () {
 	mtr_error("The destination for symlink $opt_vardir does not exist")
 	  if ! -d readlink($opt_vardir);
 
-	my $dir=       shift;
 	foreach my $bin ( glob("$opt_vardir/*") )
 	{
 	  mtr_verbose("Removing bin $bin");
@@ -1997,6 +1995,19 @@ sub setup_vardir() {
     }
   }
 
+  if ( ! -d $opt_vardir )
+  {
+    mtr_verbose("Creating $opt_vardir");
+    mkpath($opt_vardir);
+  }
+
+  # Ensure a proper error message if vardir couldn't be created
+  unless ( -d $opt_vardir and -w $opt_vardir )
+  {
+    mtr_error("Writable 'var' directory is needed, use the " .
+	      "'--vardir=<path>' option");
+  }
+
   mkpath("$opt_vardir/log");
   mkpath("$opt_vardir/run");
   mkpath("$opt_vardir/tmp");