[api] Fix wrong cache for api readState at tip height

[envestcc]

Description

The key used for interface caching is the "height" string. When an empty value is passed for the height in the query, it means to retrieve the data of the latest height. This causes the data for the latest height to still return the data for the old height.

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [] make test
• [] fullsync
• [] Other test (please specify)

Test Configuration:

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

• [] My code follows the style guidelines of this project
• [] I have performed a self-review of my code
• [] I have commented my code, particularly in hard-to-understand areas
• [] I have made corresponding changes to the documentation
• [] My changes generate no new warnings
• [] I have added tests that prove my fix is effective or that my feature works
• [] New and existing unit tests pass locally with my changes
• [] Any dependent changes have been merged and published in downstream modules

[sonarcloud[bot]]

Quality Gate failed

Failed conditions
7.9% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud