Select tenant popup only appears when mutli-tenacy is enabled (#965)

The current behavoir is that all users will see a message to switch
tenants and if multi-tenancy is disabled, that message will be prompting
the user to ask the admin to enable the feature.  This is causing users
pain that are not interested in using the tenancy features.

Signed-off-by: Peter Nied <[email protected]>
(cherry picked from commit ec59de0)

public/apps/account/account-nav-button.tsx

@@ -66,7 +66,8 @@ export function AccountNavButton(props: {
     [props.config, props.coreStart]
   );
 
-  if (getShouldShowTenantPopup()) {
+  // Check if the tenant modal should be shown on load
+  if (props.config.multitenancy.enabled && getShouldShowTenantPopup()) {
     setShouldShowTenantPopup(false);
     showTenantSwitchPanel();
   }