who has suffered an injury or contracted a disease in line of duty while en route to or from, or at, a place for final acceptance or entry upon active duty, will, for the purposes of chapters 11, 13, 19, 21, 31, and 39 of this title, and for purposes of determining service-connection of a disability under chapter
17 of this title, be considered to have been on active duty and to have incurred such disability in the active military, naval, or air service.