Update target region of packer image build. (#94)

it/packer/sonar-scanner-cli-qa.json

@@ -14,7 +14,7 @@
       "metadata": {
         "windows-startup-script-cmd": "winrm quickconfig -quiet & net user /add packer_user & net localgroup administrators packer_user /add & winrm set winrm/config/service/auth @{Basic=\"true\"}"
       },
-      "zone": "europe-west3-a",
+      "zone": "us-central1-a",
       "tags": ["packer"]
     }
   ],