feat(client): write .last-upload.results also after non-legacy uploads

[ptoscano]

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Complete Description of Additions/Changes:

While that file is deprecated and it is good that it is not written after non-legacy uploads, in practice it is actually used by tooling that uses insights-client.

To avoid breaking functionalities in other software when switching to non-legacy, write /etc/insights-client/.last-upload.results also after non-legacy uploads. While those softwares are fixed to not rely on that file, at least this is one small step ahead in switching the default away to non-legacy without regressions elsewhere.

Implements CCT-710