Add :redis keyword to some specs clear state of trackable attributes

The specs that rely on a correct value of the trackable attributes, should
include the `:redis` keyword in the spec to ensure the state is reset between
various specs.

The trackable attributes being:

- sign_in_count      : Increased every time a sign in is made (by form, openid, oauth)
- current_sign_in_at : A timestamp updated when the user signs in
- last_sign_in_at    : Holds the timestamp of the previous sign in
- current_sign_in_ip : The remote ip updated when the user sign in
- last_sign_in_ip    : Holds the remote ip of the previous sign in

The limiting of writing trackable attributes was introduced in
gitlab-org/gitlab-ce!11053.