Move the checkhandshake.pm module into test/testlib

Move this module into the same place as other test helper modules. It
simplifies the code and keeps like things together.

Perl changes reviewed by Richard Levitte. Non-perl changes reviewed by Rich
Salz

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>