This just gets ctr.config.Spec.Process.Terminal with some null checks,
allowing several places that open-coded this to use the helper.
In particular, this helps the code in
pkg/domain/infra/abi/terminal.StartAttachCtr(), that used to do:
`ctr.Spec().Process.Terminal`, which looks fine, but actually causes
a deep json copy in the `ctr.Spec()` call that takes over 3 msec.
[NO NEW TESTS NEEDED] Just minor performance effects
Signed-off-by: Alexander Larsson <alexl@redhat.com>
1038f063e0