Fix context leak when socket is not cloed explicitly

[nataraj-hates-MS-for-stealing-github]

Fix memory leak described in #469.

If this patch is applied, this module build with ASan enabled no longer fails on following sample:

use strict;
use Symbol qw(gensym);
use Net::SSLeay::Handle;

my @uris = ('ya.ru', 'google.com');
#my @uris = ('google.com');

for my $uri (@uris)
{
  my $ssl = gensym();
  tie(*$ssl, "Net::SSLeay::Handle", $uri, 443);
  print $ssl "GET / HTTP/1.0\r\n\r\n";

  my $response = do { local $/ = undef; <$ssl> };
}

This does not solves all ASan related problems, but reduces failed tests from 13 to 11 for me.

PS please refer me as NATARAJ (Nikolay Shaplov) if you ever would like to mention me anywhere...