Fix retry failed confirmations only if we are not currently retrying

[tmancey]

Description

Fix retry failed confirmations only if we are not currently retrying

Steps to Reproduce

1. View an Ad (using Charles Proxy to rewrite the confirmation request so that it fails)

Actual result:

Failed confirmations are retried every-time a token is successfully redeemed

Expected result:

Failed confirmations should only retry if we are not already retrying

Reproduces how often:

Easily reproduced

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 dev channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? No
• Does the issue resolve itself when disabling Brave Rewards? No
• Is the issue reproducible on the latest version of Chrome? No

Miscellaneous Information:

[LaurenWags]

Verified passed with

Brave	0.68.130 Chromium: 76.0.3809.100 (Official Build) (64-bit)
Revision	ed9d447d30203dc5069e540f05079e493fc1c132-refs/branch-heads/3809@{#990}
OS	Mac OS X

• Verified test plan from Fix retry failed confirmations only if we are not currently retrying brave-core#2662.

Verification passed on

Brave	0.68.130 Chromium: 76.0.3809.100 (Official Build) (64-bit)
Revision	ed9d447d30203dc5069e540f05079e493fc1c132-refs/branch-heads/3809@{#990}
OS	Windows 10 OS Version 1803 (Build 17134.523)

• Verified test plan from Fix retry failed confirmations only if we are not currently retrying brave-core#2662.

Verification passed on

Brave	0.68.130 Chromium: 76.0.3809.100 (Official Build) (64-bit)
Revision	ed9d447d30203dc5069e540f05079e493fc1c132-refs/branch-heads/3809@{#990}
OS	Ubuntu 18.04 LTS

• Verified test plan from Fix retry failed confirmations only if we are not currently retrying brave-core#2662.