Inviting an existing user

[fjavierm]

When an existing user is accepting the invitation to a new register team, when the user clicks in the invitation link is taking him to the create profile page when the profile is already created.

Actual result
An invitation is sent as it is a new user and if the user accepts the invitation he needs to introduce its credential again, resetting the profile.

Expected Result
The user should just received an email notifying him it has been invited to a team and the possibility to accept or reject the invitation.

/cc @elliecraven Can you take a look to the expected result? I've just written what I think it should be but, it's your decision.
/cc @Maidment64