Add missing use File::Spec

git-svn-id: https://svn.qindel.com/repos/main/projects/qindel/QVD/src/trunk@21996 4046b530-fbad-4e16-af16-ee11f0b55167
Partial solution to #1243: use a random port for slave channel and store it in a file so that qvd-open can look it up.

git-svn-id: https://svn.qindel.com/repos/main/projects/qindel/QVD/src/trunk@22001 4046b530-fbad-4e16-af16-ee11f0b55167