product-build.yml: use new VSTS YAML syntax

build/tfs/product-build.yml

-phases:
-- phase: Windows
+jobs:
+- job: Windows
   condition: eq(variables['VSCODE_BUILD_WIN32'], 'true')
-  queue: Hosted VS2017
+  pool:
+    vmImage: VS2017-Win2016
   variables:
     VSCODE_ARCH: x64
   steps:
   - template: win32/product-build-win32.yml
 
-- phase: Windows32
+- job: Windows32
   condition: eq(variables['VSCODE_BUILD_WIN32_32BIT'], 'true')
-  queue: Hosted VS2017
+  pool:
+    vmImage: VS2017-Win2016
   variables:
     VSCODE_ARCH: ia32
   steps:
   - template: win32/product-build-win32.yml
 
-- phase: Linux
+- job: Linux
   condition: eq(variables['VSCODE_BUILD_LINUX'], 'true')
-  queue: linux-x64
+  pool: linux-x64
   variables:
     VSCODE_ARCH: x64
   steps:
   - template: linux/product-build-linux.yml
 
-- phase: Linux32
+- job: Linux32
   condition: eq(variables['VSCODE_BUILD_LINUX_32BIT'], 'true')
-  queue: linux-ia32
+  pool: linux-ia32
   variables:
     VSCODE_ARCH: ia32
   steps:
   - template: linux/product-build-linux.yml
 
-- phase: macOS
+- job: macOS
   condition: eq(variables['VSCODE_BUILD_MACOS'], 'true')
-  queue: Hosted macOS Preview
+  pool:
+    vmImage: macOS 10.13
   steps:
-  - template: darwin/product-build-darwin.yml
\ No newline at end of file
+  - template: darwin/product-build-darwin.yml