We were previously creating our device *before* initializing the
FeaturesVk fields. This means we weren't requesting the MAINTENANCE1
extension correctly. Moving feature init before the first createDevice
call fixes the ordering issue.

This unblocks the viewport flip behaviour fixes.

Bug: angleproject:2673
Change-Id: Iae6973b57bcb4da78134a17b0644cd248bfb4981
Reviewed-on: https://chromium-review.googlesource.com/1133920Reviewed-by: Luc Ferron <lucferron@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>