Zuul: add run attribute

A proposed change[1] to Zuul removes the implied run attribute.
Add an explicit run attribute here to prepare for that.

[1] Ia8f23bce9898cd4f387554e6787b091b63e75519

Change-Id: I1fbc36c3d1b8c4ed70fceef1c587255dad50da04
1 file changed