Estimated pending rewards drops to 0 after tokens redeemed

[LaurenWags]

Description

Found while testing #5175

Estimated pending rewards dropped to 0 after tokens were redeemed on the server.

Steps to Reproduce

1. Start from a clean profile and trigger an ad
2. Quit the browser.
3. Go to something like https://www.unixtimestamp.com/ and find a timestamp a couple of minutes from now
4. Under Default/rewards_service/confirmations.json change the field "next_token_redemption_date_in_seconds" to have that new time. This will force a payment token cash in sooner.
5. Start the browser back up and wait until after the timestamp
6. If you have Rewards page open, note that your estimated pending rewards doesn't change once tokens are cashed in.
7. Refresh Rewards page.

Actual result:

Estimated pending rewards gets reset to 0

Expected result:

Estimated pending rewards should not get reset to 0

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.67.117 Chromium: 76.0.3809.62 (Official Build) (64-bit)
Revision	7b77856b3aa34d72f246d12340fc1ded8b2c0e83-refs/branch-heads/3809@{#798}
OS	Mac OS X

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the dev channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[GeetaSarvadnya]

The issue is Reproducible on Windows 10 x64

Brave	0.67.117 Chromium: 76.0.3809.62 (Official Build) (64-bit)
Revision	7b77856b3aa34d72f246d12340fc1ded8b2c0e83-refs/branch-heads/3809@{#798}
OS	Windows 10 OS Version 1803 (Build 17134.523)

[LaurenWags]

Added milestone and assignment per discussion with @jsecretan and @tmancey - if needed please adjust these.

cc @kjozwiak

[LaurenWags]

Should be solved by #5011 . We need to recheck this issue once uplift of #5011 is complete.

[LaurenWags]

Verified passed with

Brave	0.67.119 Chromium: 76.0.3809.72 (Official Build) (64-bit)
Revision	5a04c669126f657f98824b436555cae41b8f4146-refs/branch-heads/3809@{#897}
OS	Mac OS X

• Verified STR in description

Verification passed on

Brave	0.67.119 Chromium: 76.0.3809.72 (Official Build) (64-bit)
Revision	5a04c669126f657f98824b436555cae41b8f4146-refs/branch-heads/3809@{#897}
OS	Windows 10 OS Version 1803 (Build 17134.523)

• Verified the STR mentioned in the description

Verification passed on

Brave	0.67.119 Chromium: 76.0.3809.72 (Official Build) (64-bit)
Revision	5a04c669126f657f98824b436555cae41b8f4146-refs/branch-heads/3809@{#897}
OS	Ubuntu 18.04 LTS