estimated pending rewards does not reset to expected value when you have uncashed in tokens - follow up to #16678

[LaurenWags]

Description

Fix for #16678 works great, except when a user has uncashed in tokens. In the likely event that a user has tokens which have not been cashed in with the server, this will not work. So a user will still see incorrect pending BAT for current month.

Steps to Reproduce

1. Have a profile in the bad state with uncashed in tokens
2. Launch with 1.28.46
3. Look at UI and logs

Actual result:

ads panel UI does not accurately reflect estimated pending BAT (for current month or the coming ad grant)

logs still show

[21660:775:0701/163623.792441:INFO:ad_rewards.cc(280)] Payment balance is not ready
[21660:775:0701/163623.792517:VERBOSE1:ad_rewards.cc(355)] Failed to reconcile ad rewards

Expected result:

Ads panel UI to be correct, no such messages in logs

Reproduces how often:

100% for my personal case

Brave version (brave://version info)

Brave	1.28.46 Chromium: 92.0.4515.70 (Official Build) nightly (x86_64)
Revision	2df01a82398e62190b2aae01aaad7ca3d47aba01-refs/branch-heads/4515@{#923}
OS	macOS Version 10.15.7 (Build 19H1217)

Version/Channel Information:

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

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:

cc @tmancey @kjozwiak @jsecretan

[kjozwiak]

@brave/legacy_qa please leave this one as we're planning on uplifting this into 1.26.x. @LaurenWags will run through this one once we get a new 1.27.x dev build created.

[LaurenWags]

Reverted, marked QA/No per https://bravesoftware.slack.com/archives/CHGKGMHDJ/p1625774492272100?thread_ts=1625143188.230600&cid=CHGKGMHDJ