Description of problem:
Ovirt's 4.0 authentication framework makes connections to itself over https. This fact adds a new requirement on https setup on engine: the web certificate must be verified as trusted so engine-setup should validate if http service SSL configuration works OK. This might be difficult to do by looking into server configuration (there are at least three TLS modules for apache/httpd, there are other HTTP servers around, the HTTP server might run on different machine) but if we make assumptions that:

1) SSL is configured on the web server
2) http server is running before engine-setup runs
3) engine-setup is given FQDN early in the process
4) java and python trust the same certificates for 3 years already [1]

then engine-setup can verify certificate presence in black-boxy way: just do HTTP get on https://fqdn/ [2]. When this HTTP GET passes, engine-setup knows that engine will trust connection to itself so SSO will work, if not, admin can be warned of problems in advance.

[1] https://fedoraproject.org/wiki/Features/SharedSystemCertificates
[2] on RHEL 7: verification must be turned on explicitly


Version-Release number of selected component (if applicable):
rhev 4.0.0-0.6

How reproducible:
always

Steps to Reproduce:
1. configure mod_ssl to use certificate issued by CA unknown to system
2. run engine-setup with Apache SSL set to Manual
3. log in as admin@internal

Actual results:
(both in engine.log and web UI after logging form)
server_error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Expected results:
engine-setup will warn admin about incorrect SSO configuration (or unreachable web server) during step 2


Additional info:
can't be tested until bug 1336838 gets fixed

--------------------------------------------

server name validation in 2.7 can be turned on e.g. this way:
import urllib2, ssl
ctx = ssl.create_default_context()
url = ''.join('https://', fqdn, '/')
try:
    urllib2.urlopen(url, context = ctx)
except ssl.CertificateError, urllib2.URLError:
    # web server not running or with wrong certificate ...