use define instead of class for site_stunnel::setup (#3817)

so it can be called multiple times
deploy default x509::ca leap_ca in site_config::default (#3817)
remove x509::ca for leap_ca in site_openvpn::keys and site_stunnel::stunnel (#3817)
Deploy default x509 cert + key that services can use (Feature #3836)
setup stunnel config to use default x509 cert,key+ca (#3837)

* fix stunnel setups for couchdb, mx, webapp services
Merge branch 'feature/3817_3836_3837_Duplicate_declarations' into develop