Improve Jenkins / Jiro CBI build stability

Jenkins and Nexus stability have been quite poor recently. The root cause is a storage device that is beyond its capacity. The EF Releng team has cleared the roadblocks that were blocking the migration to a more stable, robust and scalable storage, and has already migrated 21 of the 240 instances.

This issue is to communicate that the team is aware of the issues, and to communicate progress.

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