quickstart.sh fails to properly pass extra script arguments

Bug

When attempting to pass extra arguments (such as an overrides file) as described in the documentation:

bash quickstart.sh -- -f values.yaml

... we get a confusing failure:

Error: "helm upgrade" requires 2 arguments

Usage: helm upgrade [RELEASE] [CHART] [flags]

7aabc243bf8f5a4cb11a95cf69ef2cfbd6e66e2b