Fixes unable to get ad tokens if tokens are not ready - 1.4.x

[tmancey]

Fixes brave/brave-browser#7666
Uplift of #4334

[kjozwiak]

Restarting Linux due to https://ci.brave.com/job/brave-browser-build-pr/job/issues%252F7666-1.4.x/1/execution/node/502/log/ failing. This is a known intermittent issue that's not related to this specific PR. However, because macOS is being restarted, I'll just restart Linux as well.

Restarting macOS due to https://ci.brave.com/job/brave-browser-build-pr/job/issues%252F7666-1.4.x/1/execution/node/706/log/ failing.

Restarting https://travis-ci.org/brave/brave-core/jobs/634490808 a it also failed.

[kjozwiak]

@tmancey once we a have Nightly that's >=1.5.23, can you double check and make sure the original PR is working as expected? Once that's completed, can you also add the below checklist into #4336 (comment).

Approved, please ensure that before merging: 
- [ ] You have checked CI and the builds, lint, and tests all pass or are not related to your PR. 
- [ ] You have tested your change on Nightly. 
- [ ] The PR milestones match the branch they are landing to. 

After you merge: 
- [ ] The associated issue milestone is set to the smallest version that the changes is landed on.

QA will also go through the original PR on Nightly to make sure things are working as expected. If everything looks good on our side, we'll start the uplift process.

[tmancey]

@kjozwiak

• You have checked CI and the builds, lint, and tests all pass or are not related to your PR.
• You have tested your change on Nightly.
• The PR milestones match the branch they are landing to.

After you merge:

• The associated issue milestone is set to the smallest version that the changes is landed on.

[kjozwiak]

Uplift into 1.4.x approved after deliberating with @brave/uplift-approvers. Both CI/Jenkins and CI/Travis passed without any issues after several restarts. Please make sure that all the correct labels are being used and the associated issue is moved into the correct milestone.