Moved some of the docker image functions to testutil.go.
Test runsc commands create, start, stop, pause, and resume.
PiperOrigin-RevId: 204138452
Change-Id: Id00bc58d2ad230db5e9e905eed942187e68e7c7b
Common code to setup and run sandbox is moved to testutil. Also, don't
link "boot" and "gofer" commands with test binary. Instead, use runsc
binary from the build. This not only make the test setup simpler, but
also resolves a dependency issue with sandbox_tests not depending on
container package.
PiperOrigin-RevId: 199164478
Change-Id: I27226286ca3f914d4d381358270dd7d70ee8372f