Generate new vars store before running unit tests

- This will increase current test runs (approx. ~4min) by one minute,
  but should reduce the likelyhood of tests ballooning up to 9+ minutes.
- Will monitor this change over a week to see if any significant changes
  show up.

[finishes #170886776](https://www.pivotaltracker.com/story/show/170886776)

Author: vitreuz

.gitignore

@@ -2,3 +2,6 @@ deployment-vars.yml
 tmp
 *hidden*
 .idea
+
+/* vars-store for unit tests */
+units/test-vars-store.yml

units/helpers/check_interpolation.go

@@ -121,7 +121,7 @@ func checkInterpolate(cfDeploymentHome, operationsSubDir, opsFileName string, op
 }
 
 func createTempVarsStore(cfDeploymentHome string) (string, error) {
-	varsStorePath := filepath.Join(cfDeploymentHome, "scripts", "fixtures", "unit-test-vars-store.yml")
+	varsStorePath := filepath.Join(cfDeploymentHome, "units", "test-vars-store.yml")
 
 	varsStoreFile, err := os.Open(varsStorePath)
 	if err != nil {

units/test

@@ -18,5 +18,11 @@ function suites() {
 }
 
 pushd "$(dirname "$0")" > /dev/null
+  if [ ! -f "test-vars-store.yml" ]; then
+    echo "Generating vars-store..."
+    bosh interpolate ../cf-deployment.yml --vars-store test-vars-store.yml > /dev/null
+  fi
+
+  echo "Starting unit tests..."
   go test "$@" $(suites) -mod=vendor
 popd > /dev/null