Dirtying the state unnecessarily was causing Vulkan backend to create
new framebuffer objects when it didn't need to.

Bug: b/174700581
Change-Id: I74e0ed51a2c6598ab3dca9a955c247ec97b6856f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2570201
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>