pre-built kernel with FUSE enabled for integration testing

[ginglis13]

For now, we've added building a kernel with FUSE enabled as a step ran in every integration test on Buildkite (#659). This adds about 1-2 minutes to the overall build time. Ideally, we would like to have a pre-built kernel that we download for integration testing, like the previous behavior with default-vmlinux:

firecracker-containerd/Makefile

Lines 211 to 216 in 3f792eb

	DEFAULT_VMLINUX_NAME?=default-vmlinux.bin
	$(DEFAULT_VMLINUX_NAME):
	curl --silent --show-error --retry 3 --max-time 30 --output $@ \
	"https://s3.amazonaws.com/spec.ccfc.min/img/quickstart_guide/$(host_arch)/kernels/vmlinux.bin"
	echo "$(kernel_sha256sum) $@" | sha256sum -c -
	chmod 0400 $@