Migrate CBS lookaside cache to new RDU3/DC

CentOS Infra issue/request

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Feature Request - something you'd like us to add/modify/change
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Description

Due to upcoming DC move, we need to migrate the https://src.sigs.centos.org lookaside cache server to new RDU3 DC, but also in parallel ensure that isolated koji builders (without any internet access) have a way to retrieve from new DC (either existing RDU2 hosts or new ones in RDU3)

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