Add .cfg suffix on build node file for consistency

All file names except this one end in .cfg so rename to match

Signed-off-by: Lott, Christopher (cl778h) <cl778h@att.com>
Change-Id: Ia1e4eeb44c2aeccfd753af8c2bdce850f2ed8c11

diff --git a/jenkins-config/clouds/openstack/cattle/centos7-builder-1c-1g b/jenkins-config/clouds/openstack/cattle/centos7-builder-1c-1g.cfg
similarity index 100%
rename from jenkins-config/clouds/openstack/cattle/centos7-builder-1c-1g
rename to jenkins-config/clouds/openstack/cattle/centos7-builder-1c-1g.cfg