Fix wrong method fee free allowances for balance less than threshold

[jason-aelf]

Closes #3359

[vizipi]

Pull request analysis by VIZIPI

Below you will find who is the most qualified team member to review your code.
This analysis includes his/her work on the code included in this Pull request, in addition to their experience in code affected by these changes ( partly found within the list of potential missing files below )   Feedback always welcome

Reviewers with knowledge related to these changes

Match %	Person	Commit Count	Common Files
100.00 %	EanCuznaivy	123	1
100.00 %	weili	88	1
100.00 %	Napoleon Wang	13	1
100.00 %	kaiwenzhengaelf	5	1
100.00 %	ssun0121	4	1
100.00 %	wangyue	2	1

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Potential missing files from this Pull request

files commonly committed with a subset of this pr, but not committed this time. (click to collapse)

File	Percentile	rate
protobuf/token_contract.proto	40.97 %	127 out of 310 times

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Committed file ranks

(click to expand)

99.94%[contract/AElf.Contracts.MultiToken/TokenContract_Fees.cs]

[codecov]

Codecov Report

Merging #3361 (d94588f) into master (3906a55) will decrease coverage by 0.04%.
The diff coverage is 66.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3361      +/-   ##
==========================================
- Coverage   91.05%   91.01%   -0.04%     
==========================================
  Files         619      619              
  Lines       23682    23684       +2     
  Branches     2093     2094       +1     
==========================================
- Hits        21563    21557       -6     
- Misses       1988     1996       +8     
  Partials      131      131              

Impacted Files	Coverage Δ
...ct/AElf.Contracts.MultiToken/TokenContract_Fees.cs	92.08% <66.66%> (-0.99%)	⬇️
.../AElf.Contracts.MultiToken/TokenContract_Helper.cs	79.68% <0.00%> (-0.53%)	⬇️