Fix format of MAAS curtin:xenial:amd64

Change-Id: I9884aa33508ea5097f88e0e138f7577166c9a57d
Related-bug: PROD-25243 (PROD:25243)
(cherry picked from commit e5a5bb51287bad1e6b3724d2c59eb9ecd90c53e8)
1 file changed