Refactor OpenVPNService state detection code

Refactor OpenVPNService state detection code

The code was standardized to avoid "E1072: a declaration cannot have a
label" warning of Visual Studio 2017 IntelliSense.

Furthermore, a comment explaining what `dwStartType <=
SERVICE_AUTO_START` condition is about.

This patch follows Gert's recommendations from [openvpn-devel].

Signed-off-by: Simon Rozman <simon@rozman.si>
Message-ID: <201901181944.x0IJiGuV003728@chekov.greenie.muc.de>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20190224181544.17232-1-simon@rozman.si>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg18233.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>