T5683: Fix reverse-proxy PKI filenames mismatch

The current named for certificates are hardcoded in generated config to:

• ca.pem
• cert.pem.key
• cert.pem

It cause a generated config certificates and certificates itself
are different (test-cert-1.pem and ca.pem)

bind :::8080 v4v6 ssl crt /run/haproxy/test-cert-1.pem

/run/haproxy/ca.pem

It is a bug of initial impelemtation. Fix required correct names
from PKI certificates

(cherry picked from commit 0431f1b32c1fc90de82adea5a7e63dad1416c340)