attention % values for sites visited after contribution are incorrect

[LaurenWags]

Description

After a contribution occurs, the Auto-Contribute table is cleared as expected. However, when you visit sites and they are added back to the table, the % values aren't adding up to 100.
Found while testing #1501

Steps to Reproduce

1. clean profile
2. enable rewards
3. claim grant
4. Close Brave. Update reconcile stamp in ledger_state file (I used current time + 15 minutes)
5. Reopen Brave.
6. visit some sites so that they are added to the table (note % values add up to 100)
7. wait for contribution
8. make sure that table is cleared and reconcile stamp is updated
9. Visit some sites and verify they are added to the table. Look at Attention % values.

Actual result:

% values aren't recalculated so that they all add up to 100%

Expected result:

% values should add up to 100%

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.55.16 Chromium: 70.0.3538.54 (Official Build) (64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Mac OS X

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds? n/a - code is not there at this time
• Does it reproduce on browser-laptop? n/a

Website problems only:

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

Additional Information

cc @NejcZdovc
cc @brave/legacy_qa for verification on other platforms

[NejcZdovc]

@kjozwiak possibly fixed with #1701

[NejcZdovc]

@LaurenWags please re-check after hotfix 2

[kjozwiak]

@kjozwiak possibly fixed with #1701

I couldn't check this reliably because I kept running into #1796.

@LaurenWags please re-check after hotfix 2

@LaurenWags is on PTO till next week so I'll go through #1796 and this issue once we get a RC 👍

[NejcZdovc]

will close and we can reopen if it's still a problem

[LaurenWags]

Verified passed with

Brave	0.56.8 Chromium: 70.0.3538.77 (Official Build) (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	Mac OS X

• Verified STR from description (used flags for --rewards-env=stag and --rewards-reconcile-interval=10 instead of manually changing the stamp)

Verification Passed on

Brave	0.56.8 Chromium: 70.0.3538.77 (Official Build) (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	Linux

• Verified STR with --rewards-env=stag --rewards-reconcile-interval=4

Verification Passed on

Brave	0.56.8 Chromium: 70.0.3538.77 (Official Build) (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	Windows

• Verified the STR on staging env using BraveSoftware/Brave-Browser/Application/brave.exe --rewards-env=stag --rewards-reconcile-interval=10