Similar to what was done in 457cdce61d, and for the same reason.
However, instead of waiting and fixing them one by one as we see them fail, I
decided to go about it more systematically. To do that, I added calls to
`time.Sleep(1 * time.Second)` in all the Shell.Commit* helper functions; this
ensures that all the commits we make get different committer time stamps, making
all these tests fail. With this I'm pretty confident that we're good now.
bf19475733