Bug 4309: Fix the presence of extensions detection in SSL Hello messages

Bug 4309: Fix the presence of extensions detection in SSL Hello messages

RFC5246 section 7.4.1.3 (Server Hello) says:

   The presence of extensions can be detected by determining whether
   there are bytes following the compression_method field at the end of
   the ServerHello.

Current parsing Hello code checks whether there are bytes in the whole SSL
message. It does not account for the fact that the message may contain more than
just ServerHello.
This patch fixes this issue and try to improve the related code to avoid related
problems in the future.

This is a Measurement Factory project