https://github.com/kubernetes/helm/pull/3183 added a keepalive to the Helm client of 30s period, while Tiller was never configured to permit this, keeping the default minimum keepalive period of 5 minutes, disconnecting any clients which ping more regularly than this.

This commit enforces a minimum that is lower than what Helm is configured for, preventing these disconnections, and thus fixes #3409.

(cherry picked from commit 588f7a84)