recompute has-permissions helper on permission service attr change

[meirish]

Previously, if a user was in a namespace, and switched - the navigation would stay the same as the previous namespace because the main nav doesn't get re-rendered and the has-permission helper shows the stale value. Now, we call the helper's recompute method when attributes on the permission service change.

To test using Vault Enterprise:

1. create a namespace (I did one called “test”)
2. enable userpass, create a user, and log in with them - give the user the default policy
3. create a policy called “test-admin” where the content is path "test/*" { capabilities = [ "create", "read", "list", "delete", "update" ] }
4. log in with the userpass user so that Vault generates an entity
5. (I did this in the UI) look up the entity and edit it - where it asks what policies to assign, add the test-admin policy
6. log in with the user in the root namespace
7. switch to the “test” namespace
8. the "Policies" tab should show up in the test namespace and disappear in the root namespace

[madalynrose]

manually tested! looks great!