CF valid_range not respected in data visualisation

[forman]

Expected behavior

When turning spatial dataset variables into RGB image tiles, the variable attribute valid_range (or one of valid_min and valid_max) should be respected. Values out of that range should be treated like NaN and turned into fully transparent pixels.

Actual behavior

valid_range (or one of valid_min and valid_max) are not respected and therefore values out of that ranges are color mapped as usual.

Steps to reproduce the problem

1. Open Land Cover CCI NetCDF
2. Select variable lccs_class
3. See all the white areas which are actually flagged as no-data

Specifications

Cate Desktop 2.0.0-dev.1