ipa-client discovery with anonymous access off

When RootDSE could be read (nsslapd-allow-anonymous-access set to
"rootdse"), autodiscovery module failed to report success to the
client installer.

Remove faulty "verified_servers" flag from autodiscovery module as
it has no point since we consider both scenarios (IPA server with
anonymous access on and unknown LDAP server with anonymous access
off) as success.

https://fedorahosted.org/freeipa/ticket/3519