IPDK doesn't clean up QEMU VMs in Networking demo

[jokuniew]

Problem statement

During networking demo there are two QEMU VMs created - VM1_TAP_DEV and VM2_TAP_DEV.

First of all - networking demo still does not have stop-demo method, so the VMs are never cleaned up after ipdk demo If user want to restart demo -> it has to kill -9 qemu processes by itself.

Possible solutions

1. Add command pkill qemu to rundemo.sh around "cleanup from previous run" here

2. Implement stop-demo in makefile just like networking_ebpf has

[jokuniew]

Also ipdk stop on networking vagrant-container solution returns given errors

root@ubuntu2004:/git/ipdk/build# ./ipdk stop
Loaded /git/ipdk/build/scripts/ipdk_default.env
Loaded /root/.ipdk/ipdk.env
qemu-system-x86_64: Failed to read from slave.
qemu-system-x86_64: Failed to read from slave.
qemu-system-x86_64: Failed to set msg fds.
qemu-system-x86_64: vhost VQ 0 ring restore failed: -1: No such file or directory (2)
qemu-system-x86_64: Failed to set msg fds.
qemu-system-x86_64: vhost VQ 1 ring restore failed: -1: No such file or directory (2)
qemu-system-x86_64: Failed to set msg fds.
qemu-system-x86_64: vhost VQ 0 ring restore failed: -1: No such file or directory (2)
qemu-system-x86_64: Failed to set msg fds.
qemu-system-x86_64: vhost VQ 1 ring restore failed: -1: No such file or directory (2)
ipdk

Before ipdk stop demo was working fine - no network issues or whatsoever

[n-sandeep]

This PR https://github.com/ipdk-io/ipdk/pull/273 fixes issue with qemu kill.