Rewrite remoteload_test integration tests (#4783)

* Better error message when git clone fails

* support file:// URLs

* rewrite remoteload_test

* lint and test fix

* fixes for kverey's comments

* document file:// remote load

* replace assert with require where appropriate

* add tests for file:// without git suffix

* fixes plus pr review from natasha

* fixes for review, lint

* revert changes to error handling

* fix skipped test

api/krusty/testdata/remoteload/multibase/base/pod.yaml

@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: myapp-pod
+  labels:
+    app: myapp
+spec:
+  containers:
+  - name: nginx
+    image: nginx:1.7.9