This test is for the regression fixed in #9103
Before fix
```
⇶ go test ./builder/azure/arm/... -run=TestConfigUserNameOverride
--- FAIL: TestConfigUserNameOverride (0.42s)
config_test.go:75: Expected 'c.Comm.SSHPassword' to be set to generated password, but found ""!
config_test.go💯 Expected 'UserName' to be set to 'override_winrm_username', but found "packer"!
FAIL
FAIL github.com/hashicorp/packer/builder/azure/arm 0.425s
FAIL
```
After fix
```
⇶ go test ./builder/azure/arm/... -run=TestConfigUserNameOverride
ok github.com/hashicorp/packer/builder/azure/arm 0.379s
```
* Fix variable names in error messages