issue to run redis-app through kraft

[Joe Huang]

 hi, follow the steps in https://github.com/unikraft/app-redis

cd redis/
kraft build

kraft run --target redis-qemu-x86_64-initrd --initrd ./rootfs -p 6379:6379 -- /redis.conf

it's not able to run the redis app, fatal error reported:

1. the --initrd flag is deprecated in favour of --rootfs
2. Fatal error, can't open config file '/redis.conf': Not a directory

one issue was reported:

       https://github.com/unikraft/app-redis/issues/23

Best Regards

Chaoyi Huang(Joe Huang)