Remove .nupkg.metadata file (#738)

Author: alerickson

src/code/InstallHelper.cs

@@ -774,7 +774,7 @@ private void DeleteExtraneousFiles(PackageIdentity pkgIdentity, string dirNameVe
             var nupkgSHAToDelete = Path.Combine(dirNameVersion, pkgIdString + ".nupkg.sha512");
             var nuspecToDelete = Path.Combine(dirNameVersion, pkgIdentity.Id + ".nuspec");
             var nupkgToDelete = Path.Combine(dirNameVersion, pkgIdString + ".nupkg");
-            var nupkgMetadataToDelete = Path.Combine(dirNameVersion, pkgIdString + ".nupkg.metadata");
+            var nupkgMetadataToDelete =  Path.Combine(dirNameVersion, ".nupkg.metadata");
             var contentTypesToDelete = Path.Combine(dirNameVersion, "[Content_Types].xml");
             var relsDirToDelete = Path.Combine(dirNameVersion, "_rels");
             var packageDirToDelete = Path.Combine(dirNameVersion, "package");