Refresh secrets after charm is authorized

Ensure any pending secrets backend requests are processes after
the charm is authorized for access to vault.

Also guard execution of the configure_secrets_backend handler
to when secrets relations actually exists via inspection of the
secrets.connected flag.

Change-Id: Ic0cb7786f2c02334778b1e1bf77d649d4db8c474

src/actions/actions.py

@@ -44,6 +44,7 @@ def authorize_charm_action(*args):
     action_config = hookenv.action_get()
     role_id = vault.setup_charm_vault_access(action_config['token'])
     hookenv.leader_set({vault.CHARM_ACCESS_ROLE_ID: role_id})
+    set_flag('secrets.refresh')
 
 
 def refresh_secrets(*args):

src/reactive/vault_handlers.py

@@ -407,7 +407,8 @@ def _check_vault_running():
         set_flag('failed.to.start')
 
 
-@when('leadership.is_leader')
+@when('leadership.is_leader',
+      'secrets.connected')
 @when_any('endpoint.secrets.new-request', 'secrets.refresh')
 def configure_secrets_backend():
     """ Process requests for setup and access to simple kv secret backends """