VS + CLI usability issues because VS does not save project changes to disk immediately

_From @alexkeh on September 28, 2018 23:47_

I am using Visual Studio 2017 (15.8.5). I create a .NET Core console project in order to create a simple EF Core app using SQL Server.

I add the latest production versions of Microsoft.EntityFrameworkCore.SqlServer and Microsoft.EntityFrameworkCore.Design assemblies (versions 2.1.3) into the project via NuGet. I then add the typical getting started demo using the BloggingContext EF Core sample. I save the project.

I then open the Package Manager Console in Visual Studio. I then change to the project directory. I then issue the command "dotnet ef migrations add InitialCreate -v" in order to scaffold the migration to create the initial set of tables to represent the model, which results in a failed build.

When I view Solution Explorer, the NuGet packages are missing.

As a workaround, I can close and re-open Visual Studio. The packages will now
be back in Solution Explorer. When I run the same command again, it executes
successfully.

```
Here's the verbose trace from the migrations add command with some redactions to remove personal info:
```
[SQL Server ef verbose - redacted.txt](https://github.com/aspnet/EntityFrameworkCore/files/2430038/SQL.Server.ef.verbose.-.redacted.txt)

_Copied from original issue: aspnet/EntityFrameworkCore#13447_