DeployOnBuild does not update dll with older version

When deploying using msbuild and DeployOnBuild parameter, a file (dll) which has a lower version compared to the previously published file does not get updated. Both files have the same size.

### Steps to reproduce

With following sample:

[MSBuildIssue.zip](https://github.com/Microsoft/msbuild/files/2146682/MSBuildIssue.zip)

Use following command line (adjust publishUrl to point to sample "output" folder)
```
msbuild ./Test/WebApp/WebApp.csproj /p:DeployOnBuild=true /p:PublishProfile=FolderProfile /p:publishUrl=C:/MSBuildIssue/output
```

### Expected behavior

Published project has library Common.Logging.Core version 3.3.1.
I would expect the output folder to contain Common.Logging.Core with version 3.3.1 after publish, overwriting the existing Common.Logging.Core file which has version 3.4.1.

### Actual behavior

Publish has kept the existing file Common.Logging.Core version 3.4.1 instead of updating it.

### Environment data

`msbuild /version` output: 15.7.179.6572

OS info: Windows 10

If applicable, version of the tool that invokes MSBuild (Visual Studio, dotnet CLI, etc): VS 2017