Fix some issues for Linux Vulkan build

lifecycle in GrVkGpu was tagged as uninitialized before use, and err in GrVkImage as unused.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1782453004

Review URL: https://codereview.chromium.org/1782453004
2 files changed