centos7 devstack jobs should not be run on icehouse
centos7 devstack jobs should not be run on icehouse

centos7 is not supported on icehouse, don't waste the jobs.

Change-Id: I100485a2f11558360af615596562852d3344b8cb

openstack-infra/project-config,open-switch/infra_project-config,coolsvap/project-config,coolsvap/project-config,anbangr/osci-project-config,noorul/os-project-config,openstack-infra/project-config,citrix-openstack/project-config,Tesora/tesora-project-config,citrix-openstack/project-config,Tesora/tesora-project-config,dongwenjuan/project-config,noorul/os-project-config,anbangr/osci-project-config,dongwenjuan/project-config,open-switch/infra_project-config