Locking down snap/ queue/ update status endpoints for a CDN

[srijeet0406]

What does this PR (Pull Request) do?

• This PR is not related to any Issue
  This PR adds the cdn locking capability to the snap/ queue/ update status endpoints.

Which Traffic Control components are affected by this PR?

• Traffic Ops
• CI tests

What is the best way to verify this PR?

Make sure all the unit/ API tests pass.
Run TO and TP locally.
As user A, send an API request to grab the lock for a particular CDN foo.
Now, try to snap foo as user A -> this should succeed
After this, log in to TO as another user B, and try to snap foo as user B -> this should fail because A has the lock for foo
Try to snap any other CDN as user B or A -> both operations should pass
Repeat the same tests for queueing and updating status of he servers on a CDN

If this is a bug fix, what versions of Traffic Control are affected?

• master

The following criteria are ALL met by this PR

• This PR includes tests
• This PR does not include documentation
• This PR does not include an update to CHANGELOG.md
• This PR includes any and all required license headers
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information

[ocket8888]

Functionality works as described, the only failing tests are the ones that are failing currently on master due to known locale issues.