Reviewed-by: schreiberal

Reviewed-by: schreiberal

Also check whether file contents are correct for both “gnt-cluster command” and
“gnt-cluster copyfile”.

Reviewed-by: iustinp

Added tests:
- “gnt-cluster getmaster”
- “gnt-cluster version”
- “gnt-instance list”
- “gnt-instance reinstall”

Reviewed-by: schreiberal

Reviewed-by: iustinp