ipatests: allow to relax security of LDAP connection from controller to IPA host
    
    The Host.ldap_connect() method uses LDAPClient from ipapython package.
    In a3934a21 we started to use secure connection from tests controller to
    ipa server. And also 5be9341f changed the LDAPClient.simple_bind method
    to forbid password based authentiction over insecure connection.
    This makes it imposible to establish ldap connection in some test
    configurations where hostnames known to ipa server do not match ones known
    to tests controller (i.e. when host.hostname != host.external_hostname)
    because TLS certificate is issued for host.hostname and test controller
    tries to verify it against host.external_hostname.
    
    A sublass of LDAPClient is provided which allows to skip certificate check.
    
    Fixes: https://pagure.io/freeipa/issue/7960
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>