puppet: Use certbot package timer, not our own cron job.

The certbot package installs its own systemd timer (and cron job,
which disabled itself if systemd is enabled) which updates
certificates.  This process races with the cron job which Zulip
installs -- the only difference being that Zulip respects the
`certbot.auto_renew` setting, and that it passes the deploy hook.
This means that occasionally nginx would not be reloaded, when the
systemd timer caught the expiration first.

Remove the custom cron job and `certbot-maybe-renew` script, and
reconfigure certbot to always reload nginx after deploying, using
certbot directory hooks.

Since `certbot.auto_renew` can't have an effect, remove the setting.
In turn, this removes the need for `--no-zulip-conf` to
`setup-certbot`.  `--deploy-hook` is similarly removed, as running
deploy hooks to restart nginx is now the default; pass
`--no-directory-hooks` in standalone mode to not attempt to reload
nginx.  The other property of `--deploy-hook`, of skipping symlinking
into place, is given its own flog.

(cherry picked from commit 01e8f752a8)

scripts/lib/install

@@ -354,8 +354,11 @@ elif [ "$package_system" = yum ]; then
 fi
 
 if [ -n "$USE_CERTBOT" ]; then
+    # Puppet, which is run below, installs the post-deploy hook to
+    # reload nginx -- but it also installs nginx itself, so we're fine
+    # to run this now.
     "$ZULIP_PATH"/scripts/setup/setup-certbot \
-        --no-zulip-conf --method=standalone \
+        --method=standalone \
         "$EXTERNAL_HOST" --email "$ZULIP_ADMINISTRATOR"
 elif [ -n "$SELF_SIGNED_CERT" ]; then
     "$ZULIP_PATH"/scripts/setup/generate-self-signed-cert \
@@ -397,10 +400,6 @@ deploy_type = production
 version = $POSTGRESQL_VERSION
 EOF
 
-    if [ -n "$USE_CERTBOT" ]; then
-        crudini --set /etc/zulip/zulip.conf certbot auto_renew yes
-    fi
-
     if [ -n "$POSTGRESQL_MISSING_DICTIONARIES" ]; then
         crudini --set /etc/zulip/zulip.conf postgresql missing_dictionaries true
     fi