Fix empty buildinfo when using conan export-package

[czoido]

Copy of this one: #155
As commented by @getrostt in the original PR:

When building a conan package using conan export-pkg, the resulting build-info when running conan art:build-info >create is empty. This is caused by an unconditional removal of the 1st graph node in the resulting json file.

To run tests with credentials