Use eval around "rmtree" and use our own version of rmtree if it fails

sub mtr_rmtree($) {

  my ($dir)= @_;

  my $need_file_find= 0;

  mtr_verbose("mtr_rmtree: $dir");

  {

  # Try to use File::Path::rmtree. Recent versions

  # handles removal of directories and files that don't

  # have full permissions, while older versions

  # may have a problem with that and we use our own version

    local $SIG{__WARN__}= sub {

      $need_file_find= 1;

      mtr_warning($_[0]);

    };

    rmtree($dir);

  }

  if ( $need_file_find ) {

  eval { rmtree($dir); };

  if ( $@ ) {

    mtr_warning("rmtree($dir) failed, trying with File::Find...");

    my $errors= 0;