Multi-line command is reformatted on a single line

### Environment
Visual Studio 2017 15.8

### Steps to reproduce

1) Create new .net standard library project

2) Add a target to csproj:

```xml

netstandard2.0

```

3) Exclude "Class1.cs" from project (or some other operation that requires saving csproj)

4) Save project (Ctrl+S)

### Expected behavior
```xml

netstandard2.0

```

### Actual behavior
```xml

netstandard2.0

```