Verify VM is running before running tests

[red-robby]

Update the testing script to verify the QEMU VM is running before proceeding with the tests. This is done via sending commands to the QEMU Monitor.

[red-robby]

We're now using the command socat, so I've also updated the docker files. The configuration needs to be updated on CircleCI for the checks to pass.

[dayeol]

The CI doesn't automatically build the docker images for test, so if there's any new dependency, we must build the docker image manually.

Besides, why do you need socat? is it to check if the socket is open?

[red-robby]

@dayeol We're using socat to establish a connection with the socket. We send info status to the QEMU Monitor via this socket to query if the VM is running. See the relevant lines below (from travis.sh).

result=$( (echo "info status" && sleep 1) | \
	socat - unix-connect:$MONITOR_SOCKET | \
	grep -oF "running")

We could use nc (netcat) instead, but the Docker image also lacks this command.