CI: fix image name to satisfy regexp

5 jobs for ci_fix_fastbuild in 2 minutes and 9 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Precheck
canceled #2742
fast-build

00:02:09

 
  External
passed cdash:debian-unstable-gcc

passed cdash:otb-centos-superbuild-base

passed cdash:ubuntu-18.04-fast

passed cdash:ubuntu-18.04-llvm