Fix remaining relative import and enable Pylint check

Relative imports are not supported in Python 3.

Part of the work for: https://fedorahosted.org/freeipa/ticket/4985

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/install/custodiainstance.py

@@ -4,7 +4,7 @@ from ipapython.secrets.kem import IPAKEMKeys
 from ipapython.secrets.client import CustodiaClient
 from ipaplatform.paths import paths
 from ipaplatform.constants import constants
-from service import SimpleServiceInstance
+from ipaserver.install.service import SimpleServiceInstance
 from ipapython import ipautil
 from ipapython.ipa_log_manager import root_logger
 from ipaserver.install import installutils

pylintrc

@@ -39,7 +39,6 @@ disable=
     redefine-in-handler,
     redefined-builtin,
     redefined-outer-name,
-    relative-import,
     super-init-not-called,
     undefined-loop-variable,
     unnecessary-lambda,