Update Azure config

- Add Ubuntu 18.04 to OS options

azure/README-zh.md

@@ -9,7 +9,7 @@
  - Username for VPN and SSH （用户名）
  - Password for VPN and SSH （密码）
  - IPsec Pre-Shared Key for VPN （IPsec 预共享密钥）
- - Operating System Image （操作系统镜像，Debian 9 或 Ubuntu 16.04 LTS）
+ - Operating System Image （操作系统镜像，Debian 9 或 Ubuntu 18.04/16.04 LTS）
  - Virtual Machine Size （虚拟机大小，默认值： Standard_B1s）
 
 **注：** \*不要\* 在值中使用这些字符： `\ " '`

azure/README.md

@@ -9,7 +9,7 @@ Customizable with the following options:
  - Username for VPN and SSH
  - Password for VPN and SSH
  - IPsec Pre-Shared Key for VPN
- - Operating System Image (Debian 9 or Ubuntu 16.04 LTS)
+ - Operating System Image (Debian 9 or Ubuntu 18.04/16.04 LTS)
  - Virtual Machine Size (Default: Standard_B1s)
 
 **Note:** DO NOT use these special characters within values: `\ " '`

azure/azuredeploy.json

@@ -24,12 +24,13 @@
     "image": {
       "type": "string",
       "allowedValues": [
+        "ubuntu1804",
         "ubuntu1604",
         "debian9"
       ],
       "defaultValue": "debian9",
       "metadata": {
-        "description": "OS to use. Debian 9 or Ubuntu 16.04 LTS"
+        "description": "OS to use. Debian 9 or Ubuntu 18.04/16.04 LTS"
       }
     },
     "VMSize": {
@@ -59,6 +60,12 @@
     "vhdStorageType": "Standard_LRS",
     "vnetId": "[resourceId('Microsoft.Network/virtualNetworks', variables('virtualNetworkName'))]",
     "SubnetRef": "[concat(variables('vnetId'), '/subnets/', variables('subnetName'))]",
+    "ubuntu1804": {
+      "publisher": "Canonical",
+      "offer": "UbuntuServer",
+      "sku": "18.04-LTS",
+      "version": "latest"
+    },
     "ubuntu1604": {
       "publisher": "Canonical",
       "offer": "UbuntuServer",