Fix Brave Ads race condition when users reset their Brave Rewards wallet

[tmancey]

Description

Fix Brave Ads race condition when users reset their Brave Rewards wallet due to refill tokens before the wallet has fully reset associated ad state.

Steps to Reproduce

1. Reset Brave Rewards wallet

Actual result:

Race condition could occur where the first token refill is cleared and a user would need to wait for a subsequent token refill

Expected result:

First token refill should top up the users tokens

Reproduces how often:

Intermittent issue (edge case which would be very rare)

Brave version (brave://version info)

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

Miscellaneous Information:

[btlechowski]

Verification passed on

Brave	1.41.65 Chromium: 103.0.5060.42 (Official Build) nightly (64-bit)
Revision	de0d840bf9439c31bd86bf74f065c31fdf9b208d-refs/branch-heads/5060@{#667}
OS	Ubuntu 18.04 LTS

Verified test plan from brave/brave-core#13614

Verified after resetting wallet, the unblinded tokens are refilled:

[16535:16535:0615/170023.097606:VERBOSE1:refill_unblinded_tokens.cc(337)] Added 50 unblinded tokens, you now have 50 unblinded tokens
[16535:16535:0615/170023.098313:VERBOSE1:account.cc(300)] Successfully refilled unblinded tokens