Add CentOS7 CI config

4 jobs for centos-ci in 15 minutes and 39 seconds (queued for 1 minute and 24 seconds)
latest
Status Job ID Name Coverage
  Build
passed #19848
build_bionic

00:03:53

passed #19847
build_buster

00:03:15

passed #19849
build_centos_7

00:05:22

passed #19846
build_stretch

00:03:08