docker: Fix debian channel to stable

Currently there is no "testing" directory in:

http://osm-download.etsi.org/repository/osm/debian/ReleaseFIVE/dists/

Change-Id: Ib43722865573a7ec386082bd1af4375af26db108
Signed-off-by: Philippe Coval <rzr@users.sf.net>
1 file changed