Add script to wait for mattermost custom resources to come up

tests/wait.sh

+#!/bin/bash
+wait_project() {
+   # interval and timeout are in seconds
+   interval=5
+   timeout=600
+   #
+   resourcename=mattermost
+   counter=0
+   # need to remove the default "set -e" to allow commands to return nonzero exit codes without the script failing
+   set +e
+   while true; do
+      if kubectl get $resourcename -o json --namespace=$resourcename -o jsonpath='{.items[0].status.state}' | \
+         grep "^stable" 1>/dev/null
+      then
+         echo "$resourcename custom resource creation finished"
+         break
+      fi
+      sleep $interval
+      let counter++
+      if [[ $(($counter * $interval)) -ge $timeout ]]; then
+         echo "$resourcename timeout waiting $timeout seconds for resource creation" 1>&2
+         exit 1
+      fi
+   done
+   set -e
+}