Enable CentOS-7 molecule jobs

CentOS-7 molecule jobs were recently disabled [1] after start failing
in get_hash tests. The proposed fix is update ca-certificates package
to avoid SSL issues originated from expired CA certificates.

[1] https://review.opendev.org/c/openstack/tripleo-repos/+/812125

Change-Id: I6508eb0795116f0a9aa6aa8c2edc589faa2039a6
Signed-off-by: Douglas Viroel <dviroel@redhat.com>

molecule/default/molecule.yml

@@ -6,9 +6,8 @@ driver:
 platforms:
   - name: instance
     image: quay.io/centos/centos:stream8
-# Disabled for now TBD if we will/can add python2 support.
-#  - name: instance_c7
-#    image: quay.io/centos/centos:centos7
+  - name: instance_c7
+    image: quay.io/centos/centos:centos7
 provisioner:
   name: ansible
 verifier:

molecule/default/prepare.yml

@@ -0,0 +1,7 @@
+- hosts: instance_c7
+  tasks:
+    - name: Update ca-certificates
+      become: true
+      package:
+        name: ca-certificates
+        state: latest