fix maximum amt

[shawnxie999]

High Level Overview of Change

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[gregtatcam]

Should add a unit-test for this.

[shawnxie999]

we already have existing unit tests that tests if the issuer issues out more than the max. the unit test i added covered the scenario reproduced in QA that currently exhibits the wrong behavior

[gregtatcam]

Isn't this a different execution path?

[shawnxie999]

All the existing test cases hit this new if-check in rippleSend. The problem found is that during holder to holder payment, rippleCredit is called twice from 1) holder to issuer and then 2)issuer to holder. The current problem is that in the second rippleCredit call from issuer to holder, the code think the issuer is trying to issue more than the MaximumAmount. This is why I moved the check in the rippleCredit to its caller rippleSend.