travis-ci: cleanup, refactor, upgrade ssl libraries

travis-ci: cleanup, refactor, upgrade ssl libraries

Both "compiler" and "exclude" are redundant, so remove them.
Add openssl-1.0.1u to build matrix. Enable explicit apt update
(it was disabled by default in travis-ci).

Signed-off-by: Ilya Shipitsin <chipitsine@gmail.com>
--
v2: Add openssl-1.0.1u to build matrix (thanks to Steffan Karger),
Add explicit apt-get update (it was disabled by default in travis-ci)
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <20180527190057.3488-1-chipitsine@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16898.html

Signed-off-by: Gert Doering <gert@greenie.muc.de>