vscode: [createInstance] extensionManagementService depends on downloadService which is NOT registered.

Issue Type: Bug

After upgrading to Visual Studio Code v1.27.1, managing extension via the command line started to show unexpected output on STDERR:

$ code --list-extensions
[createInstance] extensionManagementService depends on downloadService which is NOT registered.
DavidAnson.vscode-markdownlint
ms-vscode.Go
stkb.rewrap
timonwong.shellcheck

Apart from the output, everything else seems to work fine as far as I can see.

VS Code version: Code 1.27.1 (5944e81f3c46a3938a82c701f96d7a59b074cfdc, 2018-09-06T09:21:47.222Z) OS version: Linux x64 4.15.0-33-generic

System Info

Item	Value
CPUs	Intel® Core™ i5-5200U CPU @ 2.20GHz (4 x 1960)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: disabled_software video_decode: unavailable_software video_encode: unavailable_software webgl: enabled webgl2: enabled
Load (avg)	3, 2, 2
Memory (System)	7.41GB (1.73GB free)
Process Argv	/usr/share/code/code .
Screen Reader	no
VM	0%

Extensions (4)

Extension	Author (truncated)	Version
vscode-markdownlint	Dav	0.20.0
Go	ms-	0.6.89
rewrap	stk	1.9.1
shellcheck	tim	0.5.1