On the state affiliation selection page, give users an option to exit

[beparticular]

In the log in refactor ticket #2706, we determined that once folks get to where they choose their state affiliation, they are effectively logged in to the system and need a way to exit this screen.

Current implementation

Possible solutions

We could do one of two things -
Show the regular header at this point and provide a log out
We decided on. - * Match the "Back to Login" link that we're using in other parts of the system

Example -

This task is done when...

• a decision has been made on which direction to go in
• Decision is: add the Back to log in link on the State Affiliation page
• this direction is approved by product

[knollfear]

This looks good. Tested in multiple browsers and with keyboard only navigation.