Put zero filler into the SSL handshake packet.

[pivanof]

According to the linked documentation at
http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::SSLRequest
SSLRequest packet should have zero filler similar to the regular handshake request,
but now the driver puts zeros only in the regular request. Luckily vanilla MySQL
doesn't rely on this zero filler and doesn't verify its presence, thus the driver worked
fine so far. But MySQL can change to rely on zeros at any point.

The problem was discovered while testing against a customized MySQL.

Description

Please explain the changes you made here.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[pivanof]

@methane can you merge the PR? I don't have write access to do it myself.

[julienschmidt]

The copyright holder is Google Inc.?

Ideally also add a simple regression test.

[pivanof]

Yes, the copyright holder is Google.

I've tried to add a test, but turned out it's a hard thing to do due to SSL authentication being a completely different code path. I've also noticed that there are no tests for SSL connections at all, probably because of the same reason. Thus I decided that it should be fine without a test for now.