cluster: Fix nil pointer reference in cluster.Run
cluster: Fix nil pointer reference in cluster.Run

Before this patch, the Run function checks whether clst.namespace
matches db namespace. However, clst is nil at the beginning. This
patch initializes clst the first time Run is called.

kayousterhout/quilt,secant/quilt,kklin/kelda,LuiseV/quilt,kayousterhout/quilt,ejj/quilt-dev,stevenlin598/quilt,quilt/quilt,mmussomele/quilt,tejasmanohar/quilt,kklin/kelda,stevenlin598/quilt,LuiseV/quilt,LuiseV/quilt,stevenlin598/quilt,kklin/quilt,mmussomele/quilt,ZhongtianWang/quilt,ejj/quilt-dev,ZhongtianWang/quilt,tejasmanohar/quilt,PenguinToast/quilt,mmussomele/quilt,PenguinToast/quilt,kelda/kelda,ejj/quilt-dev,tejasmanohar/quilt,tejasmanohar/quilt,quilt/quilt,kklin/kelda,mmussomele/quilt,secant/quilt,kklin/quilt,PenguinToast/quilt,akshayknarayan/quilt,secant/quilt,NetSys/quilt,kayousterhout/quilt,quilt/quilt,akshayknarayan/quilt,kklin/quilt,akshayknarayan/quilt,kelda/kelda,PenguinToast/quilt,NetSys/quilt,akshayknarayan/quilt,quilt/quilt,NetSys/quilt,kelda/kelda,LuiseV/quilt,mmussomele/quilt,kelda/kelda,PenguinToast/quilt,stevenlin598/quilt,stevenlin598/quilt,secant/quilt,kklin/quilt,ZhongtianWang/quilt,kklin/kelda,NetSys/quilt,secant/quilt,mmussomele/quilt,NetSys/quilt,kayousterhout/quilt,ZhongtianWang/quilt,ejj/quilt-dev,LuiseV/quilt,stevenlin598/quilt