[BUG]Network, delete option for PublicIpAddress doesn't work

Hi team,

We specified the delete option for PublicIpAddress. Later we associated the IP address to a Network Interface and attached it to the VM. When we delete the VM, PublicIpAddress doesn't get deleted.

From the response of the PublicIpAddress creation, seems delete option is not set:
Request(there's "deleteOption": "Delete"):
```json
{
"location" : "eastus",
"sku" : {
"name" : "Standard"
},
"properties" : {
"publicIPAllocationMethod" : "Static",
"publicIPAddressVersion" : "IPv4",
"idleTimeoutInMinutes" : 10,
"deleteOption" : "Delete"
}
}
```

Response(there's no delete option property):
```json
{
"name" : "pip02749cd0",
"id" : "/subscriptions/REDACTED/resourceGroups/javacsmrg76219/providers/Microsoft.Network/publicIPAddresses/pip02749cd0",
"etag" : "W/\"11e20b95-4418-4996-81ec-92aa112bae2f\"",
"location" : "eastus",
"properties" : {
"provisioningState" : "Updating",
"resourceGuid" : "65ab4357-e2f7-48da-b237-7886fcb91d64",
"publicIPAddressVersion" : "IPv4",
"publicIPAllocationMethod" : "Static",
"idleTimeoutInMinutes" : 10,
"ipTags" : [ ],
"ddosSettings" : {
"protectionMode" : "VirtualNetworkInherited"
}
},
"type" : "Microsoft.Network/publicIPAddresses",
"sku" : {
"name" : "Standard",
"tier" : "Regional"
}
}
```

cc @weidongxu-microsoft

No file or test is named in the issue. Start by locating the Azure Network PublicIpAddress API specification and compare the submitted request with the returned resource, then verify the delete option is retained and deleting the VM removes the associated public IP.

Written by the indexing model from the issue text.