fix C# net45 distribtests

Author: jtattermusch

test/distrib/csharp/DistribTest/DistribTest.csproj

@@ -62,6 +62,9 @@
     <Reference Include="Grpc.Core">
       <HintPath>..\packages\Grpc.Core.__GRPC_NUGET_VERSION__\lib\net45\Grpc.Core.dll</HintPath>
     </Reference>
+    <Reference Include="Grpc.Core.Api">
+      <HintPath>..\packages\Grpc.Core.Api.__GRPC_NUGET_VERSION__\lib\net45\Grpc.Core.Api.dll</HintPath>
+    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
     <Reference Include="System.Interactive.Async">

test/distrib/csharp/DistribTest/packages.config

@@ -6,6 +6,7 @@
   <package id="Grpc" version="__GRPC_NUGET_VERSION__" targetFramework="net45" />
   <package id="Grpc.Auth" version="__GRPC_NUGET_VERSION__" targetFramework="net45" />
   <package id="Grpc.Core" version="__GRPC_NUGET_VERSION__" targetFramework="net45" />
+  <package id="Grpc.Core.Api" version="__GRPC_NUGET_VERSION__" targetFramework="net45" />
   <package id="Grpc.Tools" version="__GRPC_NUGET_VERSION__" targetFramework="net45" />
   <package id="System.Interactive.Async" version="3.0.0" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="7.0.1" targetFramework="net45" />