update drone and bump chart testing

.drone.yml

 pipeline:
   lint-charts:
-    image: guangbo/chart-testing:v1.0.3
+    image: guangbo/chart-testing:v2.0.1-rancher1
     commands:
       - git remote add rancher-charts https://github.com/rancher/charts
       - git fetch rancher-charts master
-      - chart_test.sh --config test/.testenv --no-install
+      - ct lint --config test/ct.yaml

test/.testenv

-# The name of the Git remote to check against for changed charts
-REMOTE=rancher-charts
-
-# The name of the Git target branch
-TARGET_BRANCH=master
-
-# Chart directories separated by a space
-CHART_DIRS=(
-    charts
-    proposed
-)
-
-# Charts that should be skipped
-EXCLUDED_CHARTS=(
-)
-
-# Additional chart repos to add (<name>=<url>), separated by a space
-CHART_REPOS=(
-)
-
-# Timeout for chart installation in seconds
-TIMEOUT=600
-
-# Maintainer names in Chart.yaml are validated to be existing Github accounts, default to true
-VALIDATE_MAINTAINERS=true

test/ct.yaml

+remote: rancher-charts
+target-branch: master
+chart-dirs:
+  - charts
+  - proposed
+excluded-charts:
+chart-repos:
+helm-extra-args: --timeout 600