In `execution.Create()` I was seeing `opts.Spec` unexpectedly becoming a slice
full of nulls instead of the expected data (often this occurred at the
`s.mu.Lock()`)
https://github.com/boltdb/bolt#caveats--limitations says:
> Byte slices returned from Bolt are only valid during a transaction. Once the
> transaction has been committed or rolled back then the memory they point to
> can be reused by a new page or can be unmapped from virtual memory and you'll
> see an unexpected fault address panic when accessing it.
Since `opts.Spec` = `container.Spec` where the latter is a byte slice returned
from Bolt we must copy it. The best place to do this is when reading, so that
callers need not worry about this.
I also checked metadata/*.go for similar issues and found no others.
Signed-off-by: Ian Campbell <ian.campbell@docker.com>
961e12b736