Vulkan: Minor refactor to RendererVk::initialize.
Vulkan: Minor refactor to RendererVk::initialize.

Bug: angleproject:2314
Change-Id: Ic3fa5f8ff5a0933e22b9fd5803b7ab3fbbfd449f
Reviewed-on: https://chromium-review.googlesource.com/899686
Reviewed-by: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle