gpo: Do not get templates list on first run

gpo: Do not get templates list on first run

This is a visual fix and has no impact on functionality apart from
cleaner log messages.

The point of this is to get the list of supported templates in order to
compute a diff between the current applied templates and the updated
list, so we are able to unapply and reapply the policy in case there are
differences.

However this code path is executed on first applies as well, at which
point the root CA is not yet set up. This causes the
`get_supported_templates` call to fail, which is not a hard failure but
still pollutes the logs. In this case it's safe to avoid executing the
command as the policy will be applied regardless.

Signed-off-by: Gabriel Nagy <gabriel.nagy@canonical.com>
Reviewed-by: David Mulder <dmulder@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Mon Jan 22 16:48:57 UTC 2024 on atb-devel-224

(cherry picked from commit 8579340fc540633c13c017d896034904a8dbd55c)