AssemblyVersion clobbers Version

### Steps to reproduce

Create a file `DefaultProperties.targets` with this content:

``` xml

123

```

Create a file `Repro.csproj` with this content:

``` xml

2.0

```

Build a DLL from `Repro.csproj`.

### Expected behavior
The DLL has file version 123.

### Actual behavior
The DLL has file version 2.0.

### Environment data
`msbuild /version` output: 15.9.20.62856