This fixes following warning message by changing the default runtime
to io.containerd.runc.v2 and does not require user to set the runtime
from command line anymore.
"WARN[2021-03-17T21:11:01.441207858Z] runtime v1 is deprecated since
containerd v1.4, consider using runtime v2"
Signed-off-by: Alakesh Haloi <alakeshh@amazon.com>