v.io/x.devtools/jiri-dockergo: use runutil.Sequence.
v.io/x.devtools/jiri-dockergo: use runutil.Sequence.

Change-Id: Ide11516d9123ad83c2ceacd38f3a33a6bb3aa930

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools