Recurring issues pulling ImageBuilder from CBL Mariner

[lbussell]

CI for Mariner (both 1.0 and 2.0) has been very unreliable lately, frequently requiring multiple retries.

An example of the error pulling ImageBuilder (from Run 20230621.1). It's a dotnet-docker-nightly-playground pipeline run but this is occurring in PR validation as well.

Pulling Docker image mcr.microsoft.com/dotnet-buildtools/image-builder:2201245
Error response from daemon: Get "[https://mcr.microsoft.com/v2/"](https://mcr.microsoft.com/v2/%22): context deadline exceeded (Client.Timeout exceeded while awaiting headers)
Retry 1/5 exited 1, retrying in 1 seconds...
Error response from daemon: Get "[https://mcr.microsoft.com/v2/"](https://mcr.microsoft.com/v2/%22): context deadline exceeded
Retry 2/5 exited 1, retrying in 6 seconds...
Error response from daemon: Get "[https://mcr.microsoft.com/v2/"](https://mcr.microsoft.com/v2/%22): context deadline exceeded
Retry 3/5 exited 1, retrying in 36 seconds...
Error response from daemon: Get "[https://mcr.microsoft.com/v2/"](https://mcr.microsoft.com/v2/%22): net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
Retry 4/5 exited 1, retrying in 216 seconds...
Error response from daemon: Get "[https://mcr.microsoft.com/v2/"](https://mcr.microsoft.com/v2/%22): net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

[dotnet-issue-labeler[bot]]

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[mthalman]

I don't think this is a Mariner thing. This is just MAR. There was a recent mention of this: https://github.com/microsoft/containerregistry/issues/139#issuecomment-1601187932.

[mthalman]

[Triage] There's an active issue with MAR that they're aware of. Nothing related to our Docker infrastructure.