Quick Start: get-demo.sh does not clean podtato-head on relaunch

[oleg-nenashev]

I made a mistake and launched get-demo.sh before Istio was fully installed in https://keptn.sh/docs/quickstart/ .

Error message when Istio script was not executed

---------------------------------------------------------------------
Create a Keptn project
---------------------------------------------------------------------

keptn create project podtatohead --shipyard=./shipyard.yaml
Error: This command requires to be authenticated. See "keptn auth" for details

Error 1 on re-launch after fixing Istio

Fix: remove podtato-head

MacBook-Pro-onenashev-2:quickstart nenashev$ curl -SL https://raw.githubusercontent.com/keptn/keptn.github.io/master/content/docs/quickstart/get-demo.sh | bash
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  8729  100  8729    0     0  51046      0 --:--:-- --:--:-- --:--:-- 50750

---------------------------------------------------------------------
Downloading demo resources
---------------------------------------------------------------------

This will create a local folder ./podtato-head
git clone https://github.com/cncf/podtato-head.git --single-branch
fatal: destination path 'podtato-head' already exists and is not an empty directory.

[TannerGabriel]

@oleg-nenashev Should be fixed by the PR in the keptn/examples repository.