certdb: move IPA NSS DB install functions to ipaclient.install

The create_ipa_nssdb() and update_ipa_nssdb() depend on ipaplatform.

Move them to ipaclient.install.client as they are used only from the client
installer and ipa-restore.

https://fedorahosted.org/freeipa/ticket/6474

Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

ipaserver/install/ipa_restore.py

@@ -29,9 +29,10 @@ import itertools
 from six.moves.configparser import SafeConfigParser
 # pylint: enable=import-error
 
+from ipaclient.install.client import update_ipa_nssdb
 from ipalib import api, errors
 from ipalib.constants import FQDN
-from ipapython import version, ipautil, certdb
+from ipapython import version, ipautil
 from ipapython.ipautil import run, user_input
 from ipapython import admintool
 from ipapython.dn import DN
@@ -831,7 +832,7 @@ class Restore(admintool.AdminTool):
 
     def cert_restore(self):
         try:
-            certdb.update_ipa_nssdb()
+            update_ipa_nssdb()
         except RuntimeError as e:
             self.log.error("%s", e)