fix(@angular/cli): correctly access root workspace path

(cherry picked from commit ae04726)

Author: clydin

packages/angular/cli/commands/add-impl.ts

@@ -38,7 +38,7 @@ export class AddCommand extends SchematicCommand<AddCommandSchema> {
   }
 
   async run(options: AddCommandSchema & Arguments) {
-    await ensureCompatibleNpm(this.context.root);
+    await ensureCompatibleNpm(this.workspace.root);
 
     if (!options.collection) {
       this.logger.fatal(

packages/angular/cli/commands/new-impl.ts

@@ -22,7 +22,7 @@ export class NewCommand extends SchematicCommand<NewCommandSchema> {
   }
 
   public async run(options: NewCommandSchema & Arguments) {
-    await ensureCompatibleNpm(this.context.root);
+    await ensureCompatibleNpm(this.workspace.root);
 
     // Register the version of the CLI in the registry.
     const packageJson = require('../package.json');

packages/angular/cli/commands/update-impl.ts

@@ -256,7 +256,7 @@ export class UpdateCommand extends Command<UpdateCommandSchema> {
 
   // tslint:disable-next-line:no-big-function
   async run(options: UpdateCommandSchema & Arguments) {
-    await ensureCompatibleNpm(this.context.root);
+    await ensureCompatibleNpm(this.workspace.root);
 
     // Check if the @angular-devkit/schematics package can be resolved from the workspace root
     // This works around issues with packages containing migrations that cannot directly depend on the package