Update image name for Molecule

Sanitizing image name for Molecule testing with
new updated naming pattern.

Change-Id: I1565242f0ddd88b0df758ebb3519f2e059f22c02
Issue-ID: OOM-1774
Signed-off-by:  Bartek Grzybowski <b.grzybowski@partner.samsung.com>
diff --git a/ansible/roles/nfs/molecule/default/molecule.yml b/ansible/roles/nfs/molecule/default/molecule.yml
index 552f4bc..71e08d0 100644
--- a/ansible/roles/nfs/molecule/default/molecule.yml
+++ b/ansible/roles/nfs/molecule/default/molecule.yml
@@ -7,7 +7,7 @@
   name: yamllint
 platforms:
   - name: kubernetes-node-1
-    image: molecule-${PREBUILD_PLATFORM_DISTRO:-centos7}:${PREBUILD_DISTRO_VERSION:-latest}
+    image: molecule-${PREBUILD_PLATFORM_DISTRO:-centos}:${PREBUILD_DISTRO_VERSION:-centos7.6}
     pre_build_image: true
     privileged: true
     command: ${MOLECULE_DOCKER_COMMAND:-""}
@@ -21,7 +21,7 @@
       - ${HOME}/data:/dockerdata-nfs:rw
 
   - name: kubernetes-node-2
-    image: molecule-${PREBUILD_PLATFORM_DISTRO:-centos7}:${PREBUILD_DISTRO_VERSION:-latest}
+    image: molecule-${PREBUILD_PLATFORM_DISTRO:-centos}:${PREBUILD_DISTRO_VERSION:-centos7.6}
     pre_build_image: true
     privileged: true
     command: ${MOLECULE_DOCKER_COMMAND:-""}