ipaclient: Fix issues with FreeIPA 4.6 and prior

check_ldap_conf is only available in FreeIPA 4.7 and later and
tasks.is_nosssd_supported is only available since 4.6.90.pre2.

check_ldap_conf is None (ansible_ipa_client) if it can not be imported.
hasattr has been added to check if is_nosssd_supported is a valid
attribute in tasks.

Fixes: #61 (ipaserver role - Fails on ipaclient install)

roles/ipaclient/library/ipaclient_test.py

@@ -484,6 +484,7 @@ def main():
         #        "IPA client is already configured on this system.",
         #        rval=CLIENT_ALREADY_CONFIGURED)
 
+        if check_ldap_conf is not None:
             check_ldap_conf()
 
         if options.conf_ntp:
@@ -526,6 +527,7 @@ def main():
                 "Invalid hostname, '{}' must not be used.".format(hostname),
                 rval=CLIENT_INSTALL_ERROR)
 
+        if hasattr(tasks, "is_nosssd_supported"):
             # --no-sssd is not supported any more for rhel-based distros
             if not tasks.is_nosssd_supported() and not options.sssd:
                 raise ScriptError(