Fix show mixin image test

[JonnyWong16]

Description

• Fix the show section scanning progress bar for the bootstrap test server.
• Mark the show mixin image test as xfail. Sometimes changing show artwork fails randomly.

Type of change

Please delete options that are not relevant.

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

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the docstring for new or existing methods
• I have added tests when applicable