Improved the code style.
Improved the code style.

* Rewritten more of ssh calls into functions.
* Improved the option check message.

OpenSCAP/openscap,mpreisler/openscap,jan-cerny/openscap,redhatrises/openscap,OpenSCAP/openscap,OpenSCAP/openscap,redhatrises/openscap,mpreisler/openscap,jan-cerny/openscap,redhatrises/openscap,redhatrises/openscap,mpreisler/openscap,mpreisler/openscap,OpenSCAP/openscap,jan-cerny/openscap,redhatrises/openscap,OpenSCAP/openscap,jan-cerny/openscap,jan-cerny/openscap,OpenSCAP/openscap,mpreisler/openscap,jan-cerny/openscap,redhatrises/openscap,mpreisler/openscap