Update to FrontDoor Unintentionally Modifies Routing Rule

- If the issue is to do with Azure CLI 2.0 in-particular, create an issue here at [Azure/azure-cli](https://github.com/Azure/azure-cli/issues)

### Extension name (the extension in question)

front-door

### Description of issue (in as much detail as possible)

I updated the `--send-recv-timeout` on some frontdoors today, updating them to 60 seconds (from the default of 30).

```
az network front-door update -g MYRG -n MYFD --send-recv-timeout 60
# (1673ms < Mon Apr 6 09:40:26 2020)
```

I noticed during my next Terraform plan operation that it wanted to update a routing rule on the FrontDoor. The AzCLI command changed the redirect type on the https-redirect routing rule from 308 (PermanentRedirect) to 301 (Moved). I can see this on the change history tab in the Activity Log for the Frontdoor resource.


Potential bug?

-----

### AZ CLI Versions

```
> az version
Azure-cli Azure-cli-command-modules-nspkg Azure-cli-core Azure-cli-nspkg Azure-cli-telemetry
----------- --------------------------------- ---------------- ----------------- ---------------------
2.3.1 2.0.3 2.3.1 3.0.4 1.0.4

> az extension list
Experimental ExtensionType Name Preview Version
-------------- --------------- -------------------- --------- ---------
False whl dev-spaces False 1.0.5
False whl front-door False 1.0.6
False whl aks-preview True 0.4.42
False whl azure-devops False 0.18.0
False whl log-analytics True 0.1.4
False whl application-insights True 0.1.6
```