Fix infinite loop in get_file_device_path() in chroot environment #784.

In a chroot filesystem or if it didn't get the device for the file it will always treat it as a remotefs and cobbler will never try to create hard link in chroot filesystem.
Merge pull request #799 from santosh0705/chrootmtab

Fix infinite loop in get_file_device_path() in chroot environment #784.