openstack undercloud install exits with SSL error when using non self-signed certificates

Issue

Steps to Reproduce:
1. Create a self signed CA
2. Add the CA to the trust store
3. Create a service certificate signed by the CA
4. copy the cert pem file to /etc/pki/instack-certs
5. configure the parameter undercloud_service_certificate in undercloud.conf pointing to the cer pem file
6. run openstack undercloud install

Actual results:
the installation fails with the following error: ERROR: openstack SSL exception connecting to https://10.10.10.3:13000/v2.0/tokens: [Errno 1] _ssl.c:504: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed