Bugfix for DROOLS-354 and DROOLS-540 on 6.1.x branch (backport from master)

This pull request includes a bugfix for Drools issues DROOLS-354 and DROOLS-540 on Windows using WildFly application server.

Essentially, the problem is, that the path obtained via WildFly VFS is a path (so there is no leading "/"), but the code in IoUtils checks for the leading "/", otherwise the drive letter gets stripped creating a drive-relative path. This works well when WildFly's working directory and the VFS target file is on the same drive, but fails if two different drives are involved.