Revert "Try to use gitlab's new ability to run jobs in parallel"

This reverts commit 4972b0fe.
7 jobs for master in 2 minutes and 4 seconds
Status Job ID Name Coverage
  Build
passed #2491
apt

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passed #2492
cloudlab

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passed #2493
emulab

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passed #2494
phantomnet

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passed #2495
powder

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  Deploy
passed #2496
pages

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passed pages:deploy

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