An in-range update of grpc is breaking the build 🚨

## The dependency [grpc](https://github.com/grpc/grpc-node) was updated from `1.22.1` to `1.22.2`.

🚨 [View failing branch](https://github.com/konsumer/grpcnode/compare/master...konsumer:greenkeeper%2Fgrpc-1.22.2).

This version is **covered** by your **current version range** and after updating it in your project **the build failed**.

grpc is a direct dependency of this project, and **it is very likely causing it to break**. If other packages depend on yours, this update is probably also breaking those in turn.

Status Details

- ❌ **continuous-integration/travis-ci/push:** The Travis CI build could not complete due to an error ([Details](https://travis-ci.org/konsumer/grpcnode/builds/569179268?utm_source=github_status&utm_medium=notification)).

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Your [Greenkeeper](https://greenkeeper.io) Bot :palm_tree:

Beginne mit der Untersuchung des verlinkten fehlschlagenden Branches und der Travis CI-Builddetails, reproduziere anschließend den Fehler mit grpc 1.22.2. Ermittle die Ursache für den fehlgeschlagenen Build und überprüfe, dass das Projekt mit der Aktualisierung der Abhängigkeit erfolgreich gebaut wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.