(cam_rescan): Do not reference ccb->ccb_h.path in CAM_DEBUG call before
it is initialized; use path instead.

This change fixes a panic when using atapicam in conjunction with CAMDEBUG,
which has been described under kern/103602.

Thanks to Josh Carroll <josh.carroll@gmail.com> for providing the traces
that allowed identifying this problem.

PR: kern/103602
MFC after: 1 week