Do not restore in parallel by default

Author: dougbu

Runtime.msbuild

@@ -10,6 +10,7 @@
     <StyleCopEnabled Condition=" '$(StyleCopEnabled)' == '' ">true</StyleCopEnabled>
     <BuildPortable Condition=" '$(BuildPortable)' == '' ">true</BuildPortable>
     <BuildInParallel Condition=" '$(BuildInParallel)' == '' And $(MSBuildNodeCount) &gt; 1 ">true</BuildInParallel>
+    <RestoreInParallel Condition=" '$(RestoreInParallel)' == '' ">false</RestoreInParallel>
     <BuildInParallel Condition=" '$(BuildInParallel)' == '' ">false</BuildInParallel>
     <TestInParallel Condition=" '$(TestInParallel)' == '' ">false</TestInParallel>
     <TestResultsDirectory>$(MSBuildThisFileDirectory)bin\$(Configuration)\test\TestResults\</TestResultsDirectory>
@@ -93,7 +94,7 @@
     <!-- 2. Restore SDK-style test projects because legacy test projects depend on TestCommon. -->
     <Message Importance="High" Text='%0A&gt; dotnet restore "@(_ProjectsToRestore)"' />
     <MSBuild Projects="@(_ProjectsToRestore)" Targets="Restore"
-      BuildInParallel="$(BuildInParallel)"
+      BuildInParallel="$(RestoreInParallel)"
       Properties="Configuration=$(Configuration);CodeAnalysis=$(CodeAnalysis);StyleCopEnabled=$(StyleCopEnabled);VisualStudioVersion=$(VisualStudioVersion)" />
     <!-- 3. Restore remaining legacy projects. -->
     <Message Importance="High" Text='%0A&gt; "$(NuGetExe)" restore "@(_NuGetPackagesAndSolutions)" ...' />