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

This reverts commit 4972b0fe.
6 jobs for master in 0 seconds (queued for 95 minutes and 46 seconds)
latest
Status Job ID Name Coverage
  Build
failed #2498
apt

failed #2499
cloudlab

failed #2500
emulab

failed #2501
phantomnet

failed #2502
powder

 
  Deploy
skipped #2503
pages
 
Name Stage Failure
failed
powder Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace
failed
phantomnet Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace
failed
emulab Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace
failed
cloudlab Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace
failed
apt Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job trace