always restart chrony on a crash

Summary:
If chrony crashes it doesn't get restarted by systemd which leaves us until next chef run to restart.
This diff adds `Restart = always` directive which will resurrect the service

Differential Revision: D61338001

fbshipit-source-id: 1ad4a1422df0fb254f71576f6d1bdd3460bee487

cookbooks/fb_chrony/metadata.rb

@@ -14,3 +14,4 @@
 supports 'rocky'
 supports 'ubuntu'
 depends 'fb_helpers'
+depends 'fb_systemd'

cookbooks/fb_chrony/recipes/default.rb

@@ -50,8 +50,20 @@
   notifies :restart, 'service[chrony]'
 end
 
+fb_systemd_override 'chronyd_override' do
+  unit_name 'chronyd.service'
+  content({
+            'Service' => {
+              'Restart' => 'always',
+            },
+          })
+end
+
 service 'chrony' do
   service_name chrony_svc
   action [:enable, :start]
-  subscribes :restart, 'package[chrony]'
+  subscribes :restart, [
+    'package[chrony]',
+    'fb_systemd_override[chronyd_override]',
+  ]
 end