change kind-cluster script to bash

[aclevername]

STEP: Given I have a brand new cluster with a long cluster name
time="2022-02-09T10:56:11Z" level=info msg="Creating a kind cluster "
Create a new kind cluster with name 
./scripts/kind-cluster.sh: 22: [[: not found
Registry Host: kind-registry
ERROR: failed to create cluster: node(s) already exist for a cluster with the name "kind"
time="2022-02-09T10:56:11Z" level=info msg="Failed to create kind cluster"
time="2022-02-09T10:56:11Z" level=fatal msg="exit status 1"

https://github.com/weaveworks/weave-gitops/runs/5123765368?check_suite_focus=true

switching to bash should fix this. Also removes unneeded creating of a kind cluster in the buildup, since each test creates its own cluster