Already sustaining ad notification interaction is shown for conversion of the second ad within the same creative set

[btlechowski]

Found while testing #6536.
The conversion queue should be empty after trying the conversion of another ad with the same creative set id

Steps to Reproduce

1. Watch an ad
2. Convert the ad
3. Watch a second ad with the same creativeSetId
4. Convert the second ad
5. Watch logs

Note: reproduced on staging

Actual result:

Already sustaining ad notification interaction for https://travala.com/booking?check_in=*

Expected result:

Ads conversion queue is empty

Reproduces how often:

50% repro rate

Brave version (brave://version info)

Brave	1.7.54 Chromium: 80.0.3987.132 (Official Build) nightly (64-bit)
Revision	fcea73228632975e052eb90fcf6cd1752d3b42b4-refs/branch-heads/3987@{#974}
OS	Ubuntu 18.04 LTS

Brave	1.7.54 Chromium: 80.0.3987.132 (Official Build) nightly (64-bit)
Revision	fcea73228632975e052eb90fcf6cd1752d3b42b4-refs/branch-heads/3987@{#974}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

cc @brave/legacy_qa @tmancey @jsecretan @rebron

[btlechowski]

Verification passed on

Brave	1.8.82 Chromium: 81.0.4044.113 (Official Build) dev (64-bit)
Revision	e3225dafb0475864a1812a374d73a92e391635ac-refs/branch-heads/4044@{#936}
OS	Ubuntu 18.04 LTS

Test plan used:

1. Overwrite the catalog with Charles
   Catalog:
   8634.txt
2. Run Brave with command line: /usr/bin/brave-browser-dev --enable-logging=stderr --vmodule=brave_ads=3 --brave-ads-staging --rewards=staging=true
3. Enable Rewards
4. Open brave.com and trigger an ad
5. Click on the ad
6. Wait for the ad conversion confirmation
7. Open brave.com and trigger an ad
8. Click on the ad

Expected behavior:
Already sustaining ad notification interaction for is not in the logs

Verified above test plan.

Logged #9412

---

Verified passed with

Brave	1.8.82 Chromium: 81.0.4044.113 (Official Build) dev (64-bit)
Revision	e3225dafb0475864a1812a374d73a92e391635ac-refs/branch-heads/4044@{#936}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified test plan outlined above
• Encountered Multiple landed confirmations for the same ad view #9412

Verification passed on

Brave	1.8.84 Chromium: 81.0.4044.122 (Official Build) (64-bit)
Revision	44f4233f08910d83b146130c1938256a2e05b136-refs/branch-heads/4044@{#963}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan outlined above