Fix applying DES-CBC when using OpenSSL 3

[paulvt]

After calling #final on the cipher object, it will return garbage from that moment forward. The cipher object can therefore not be reused in the iteration over keys. Reinitialize it everytime instead.

This seems to be new behaviour in Ruby/OpenSSL3. See also:
https://ruby.github.io/openssl/OpenSSL/Cipher.html#class-OpenSSL::Cipher-label-Calling+Cipher-23final

This fixes #50.

[adfoster-r7]

We're hitting this issue with one of our Ruby gems too 👍

The work around I had before finding this pull request was:

       def apply_des(plain, keys)
         dec = OpenSSL::Cipher.new("des-cbc").encrypt
         dec.padding = 0
         keys.map {|k|
+          dec.reset
+          dec.iv = "\x00" * 8
           dec.key = k
           dec.update(plain) + dec.final
         }
       end

[adfoster-r7]

Ah, it doesn't look like this patch is available in the latest rubyntlm release on RubyGems

@mwrock It'd be great if this could be released as a patch version, let me know if I can help in anyway 🎉