MySql environment variables for Windows pkg-nodes

This will add MySql environment variables for Windows packaging nodes
including Windows 7 x86/x64 and Windows 8 x86/64

Change-Id: Ifb493a683036fb1a6874aeef235575716b5e34b0
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>