Backport 8295 "Disc Usage during Repository Sync" to 3.14.z
Move downloaded files instead of copying them
Before this commit, the condition that checks whether pulp's temporary files are stored within /var/lib/pulp was never met because it looked for files starting with /var/lib/pulp/media (MEDIA_ROOT). MEDIA_ROOT is however no longer pointing to /var/lib/pulp.
(cherry picked from commit fbe2d7f9c85008e8223fec8fcfdb87e665e06881)