Code review comment for lp://staging/~al-maisan/launchpad/observe-virtualized-507323

Hello there!

The selection of candidate jobs for idle builders in the build farm compares
the platform settings (processor/virtualized) for these.
In cases where a potential candidate job does not care about virtualization it
should only be considered for virtualized builders.
This is a security precaution preventing the execution of untrusted code on
native builders.

Please note that all _findBuildCandidate() tests (we have a pretty extensive
test coverage of the build farm candidate job selection) pass.

Test to run:

    bin/test -vv -t build

No "make lint" errors or warnings.