Fix the log output when starting the grpc gateway in the sdkserver

[roberthbailey]

So that it is clear what port is being bound for http requests.

Very minor fix, but this has been confusing for me for the last couple of days.

[google-oss-robot]

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This pull-request has been approved by: markmandel, roberthbailey
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[agones-bot]

Build Succeeded 👏

Build Id: 212bf991-b736-44a0-958b-eaa918d4ef1e

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.1.0-63a4df1
• image: gcr.io/agones-images/agones-sdk:1.1.0-63a4df1
• image: gcr.io/agones-images/agones-ping:1.1.0-63a4df1
• Linux C++ SDK (build): agonessdk-1.1.0-63a4df1-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.1.0-63a4df1.zip

A preview of the website (the last 30 builds are retained):

• https://63a4df1-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/1096/head:pr_1096 && git checkout pr_1096
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.1.0-63a4df1