cmds/core/kill: Create an unused port for testing kill
cmds/core/kill: Create an unused port for testing kill

The kill test might fail because PID 9999 exists. This commit
create a PID that will be unused temporarily for testing purpose.

Signed-off-by: Medicine Yeh <ce0f0ca58c98e036a28df53229ac3ccdc6eee9c7@gmail.com>

u-root/u-root,u-root/u-root,u-root/u-root