Fix file name handling in bundle_adjust_tracks
Fix file name handling in bundle_adjust_tracks

Fix another porting error, this time in 7bc5e90ed992, where getting the
list of files in a directory was returning only the file names, and not
the paths, as per previous behavior, and as required for us to later
load the file.

linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk