BB2-3379: Created separate waffle switch for logout flow

[stiwarisemanticbits]

JIRA Ticket:
BB2-3379

What Does This PR Do?

• Add dedicated logout waffle switch so logout can be toggled independently of login. By default its enabled
• Update both v1 and v2 account logout URLs to use the new switch

What Should Reviewers Watch For?

• Checkout this branch, and start server
• login into Django admin
• Run test client
• On the test client page, select Log out to continue
• It should now show 404
• Disbale logout waffle switch
• Try again and now we should get 404

If you're reviewing this PR, please check for these things in particular:

Validation

What Security Implications Does This PR Have?

Please indicate if this PR does any of the following:

• Adds any new software dependencies
• Modifies any security controls
• Adds new transmission or storage of data
• Any other changes that could possibly affect security?

• Yes, one or more of the above security implications apply. This PR must not be merged without the ISSO or team
  security engineer's approval.

Any Migrations?

• Yes, there are migrations
  • The migrations should be run PRIOR to the code being deployed
  • The migrations should be run AFTER the code is deployed
  • There is a more complicated migration plan (downtime,
    etc)
• No migrations

[jimmyfagan]

Looks good! We'll want to be careful during deployment to make sure these switches are in place @stiwarisemanticbits could you pre-emptively add the logout switch with the correct values to the higher environments?