local-up-cluster.sh: don't require to be invoked in the root

It's normal for shell scripts to change the current directory if they expect to
run in the repo root.

hack/local-up-cluster.sh

@@ -20,6 +20,7 @@ if (( KUBE_VERBOSE > 4 )); then
 fi
 
 KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
+cd "${KUBE_ROOT}"
 
 # This script builds and runs a local kubernetes cluster. You may need to run
 # this as root to allow kubelet to open containerd's socket, and to write the test