SDK/installer infra should not install just-built linux packages in CI builds

[mmitche]

GenerateRPMs.targets installs the RPMs it just built into the environment as a test. This is a bit problematic, because the host container may have dotnet packages installed on it already (due to tools installed by templates a build time or tools installed in the image, etc.). This may mean that the installation will fail due to an upgrade, downgrade, etc.

If the SDK wants to do this test, it should be done in another clean container and not the CI container.