Fixing the build failures from a missing GCS Key (#1480)

* Fixing the build failures from a missing GCS Key

Accidentally introduced in https://github.com/gomods/athens/pull/1428

* Adding a TODO to the drone build

* adding a step to test the Athens server startup

* Adding the JSONKey back to the default config

* use temporary image

* Switching back to the old env var for the GCS JSON Key

cc/ @marwan-at-work

* removing the ServiceAccount. we want to stick with JSONKey

* reverting to original key fetching code

* fixing build err

* bumping chart ver

pkg/stash/with_gcs_test.go

@@ -121,7 +121,7 @@ func getTestConfig() *config.GCPConfig {
 		return nil
 	}
 	return &config.GCPConfig{
-		Bucket:         "athens_drone_stash_bucket",
-		ServiceAccount: creds,
+		Bucket:  "athens_drone_stash_bucket",
+		JSONKey: creds,
 	}
 }