src/main.rs: vsock with vmm-no-api
src/main.rs: vsock with vmm-no-api

Due to the latest changes regarding the way vsock devices are actually
attached, it was no longer possible to add one using the command line
parameters. These changes re-enable that functionality, by invoking
logic that is also used when the VMM interprets incoming API requests.

Signed-off-by: Alexandru Agache <69826f943dd6ae0c808126caf67f094b6aee96c2@amazon.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker