deployment valdiate doesn't validate properly.

### Description

When calling `az group deployment validate g "test-01" --template-file .\azuredeploy.json --parameters .\azuredeploy-test-params.json`, it returns no errors. When `az group deployment create` is called with the same parameters, it fails with `InvalidRequestFormat`.

Here is a subset of the template:

```json
{
"name": "pcf",
"type": "Microsoft.Network/virtualNetworks",
"apiVersion": "2017-03-01",
"location": "[parameters('location')]",
"tags": {
"Environment": "[parameters('environment')]"
},
"properties": {
"addressSpace": {
"addressPrefixes": [
"10.0.0.0/16"
]
},
"subnets": [
{
"name": "Management",
"properties": {
"addressPrefix": "10.0.4.0/22",
"location": "[parameters('location')]",
"tags": {
"Environment": "[parameters('environment')]"
},
"properties": {
"networkSecurityGroup": {
"securityRules": [
{
"properties": {
"description": "Allow Inbound HTTP/S",
"protocol": "*",
"sourcePortRange": "*",
"destinationPortRange": "80,443",
"sourceAddressPrefix": "*",
"destinationAddressPrefix": "*",
"access": "Allow",
"priority": 1400,
"direction": "Inbound"
},
"name": "Allow-Web"
}
]
}
}
}
}
]
}
}
```

Here is an example of the failure:

```json
Deployment failed. {
"error": {
"code": "InvalidRequestFormat",
"message": "Cannot parse the request.",
"details": [
{
"code": "InvalidJson",
"message": "Could not find member 'location' on object of type 'SubnetProperties'. Path 'properties.subnets[0].properties.location', line 1, position 202."
},
{
"code": "InvalidJson",
"message": "Could not find member 'tags' on object of type 'SubnetProperties'. Path 'properties.subnets[0].properties.tags', line 1, position 218."
},
{
"code": "InvalidJson",
"message": "Could not find member 'properties' on object of type 'SubnetProperties'. Path 'properties.subnets[0].properties.properties', line 1, position 253."
}
]
}
}
```

---

### Environment summary

**Install Method:** How did you install the CLI? (e.g. pip, interactive script, apt-get, Docker, MSI, nightly)
Answer here: MSI

**CLI Version:** What version of the CLI and modules are installed? (Use `az --version`)
```powershell
PS C:\Users\MikeLloyd\Development\azure\pcf-azure-arm-templates> az --version
azure-cli (2.0.16)

acr (2.0.11)
acs (2.0.14)
appservice (0.1.15)
batch (3.1.2)
billing (0.1.4)
cdn (0.0.7)
cloud (2.0.7)
cognitiveservices (0.1.7)
command-modules-nspkg (2.0.1)
component (2.0.7)
configure (2.0.10)
consumption (0.1.4)
container (0.1.9)
core (2.0.15)
cosmosdb (0.1.12)
dla (0.0.11)
dls (0.0.13)
eventgrid (0.1.3)
feedback (2.0.6)
find (0.2.6)
interactive (0.3.9)
iot (0.1.11)
keyvault (2.0.9)
lab (0.0.10)
monitor (0.0.9)
network (2.0.13)
nspkg (3.0.1)
profile (2.0.11)
rdbms (0.0.6)
redis (0.2.8)
resource (2.0.13)
role (2.0.11)
servicefabric (0.0.3)
sf (1.0.8)
sql (2.0.10)
storage (2.0.14)
vm (2.0.13)

Python (Windows) 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 17:54:52) [MSC v.1900 32 bit (Intel)]

Python location 'C:\Program Files (x86)\Microsoft SDKs\Azure\CLI2\python.exe'

Legal docs and information: aka.ms/AzureCliLegal
```

**OS Version:** What OS and version are you using?
Answer here:

**Shell Type:** What shell are you using? (e.g. bash, cmd.exe, Bash on Windows)
Answer here:
```powershell
PS C:\Users\MikeLloyd\Development\azure\pcf-azure-arm-templates> $PSVersionTable

Name Value
---- -----
PSVersion 5.1.15063.608
PSEdition Desktop
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
BuildVersion 10.0.15063.608
CLRVersion 4.0.30319.42000
WSManStackVersion 3.0
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
```