Run CI with temporary files on a ramdisk
Run CI with temporary files on a ramdisk

This sets up a tmpfs mount to be used for temporary files created by tests.

If this works, hopefully it will fix the excessive I/O latencies that
are blocking tests for long periods and causing them to fail.

As a side effect, this also stores temporary compilation artifacts on
tmpfs.

Signed-off-by: Aaron Lehmann <8ecfc6017a87905413dcd7d63696a2a4c351b604@docker.com>

cheyang/swarmkit,AliyunContainerService/swarmkit,sungwonh/swarmkit,Noyan759/swarmkit,RenaudWasTaken/swarmkit,Noyan759/swarmkit,docker/swarmkit,alyyousuf7/swarmkit,RenaudWasTaken/swarmkit,dperny/swarmkit-1,dperny/swarmkit-1,sungwonh/swarmkit,alyyousuf7/swarmkit,AliyunContainerService/swarmkit,cheyang/swarmkit,docker/swarmkit,jlhawn/swarmkit,jlhawn/swarmkit