--upload-test-report should post comment with test report in easyblocks PR if --include-easyblock-from-pr was used

[boegel]

(but only if it's used without --from-pr)

That would be useful to have a record of with which existing easyconfigs testing was done for PRs that change existing easyblocks (like easybuilders/easybuild-easyblocks#2030 for example).

Test case, using Score-P-6.0-gompi-2019a.eb easyconfig file that is already included in EasyBuild releases:

eb Score-P-6.0-gompi-2019a.eb -f --include-easyblocks-from-pr 2030

[migueldiascosta]

in the --from-pr case, we could reference the easyblock PR in the easyconfig PR comment?