Fetch control plane IP at runtime

[anusha94]

What this PR does / why we need it:
Set the CONTROL_PLANE_ENDPOINT_IP programmatically at runtime during E2E tests based on docker network settings.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #206

[anusha94]

minor nits. Otherwise lgtm

[pshail]

small nit, rest is LGTM

[NilanjanDaw]

small nit, rest is LGTM

Hey, @pshail please Iet me know the edits required.

[pshail]

@anusha94 just suggested the other way round 🙃 ... sorry for this @NilanjanDaw i just saw the resolved comments
lets go ahead with this - its anyway a nit 😉

[jamiemonserrate]

LGTM

[huchen2021]

I don't have strong opinion about this. But I feel a little concern about this hard code way, it looks like a potential bug may occurs one day in the future. It will be better if we can do this more smart. What I can think of is as followed, just for refer:

1. Fetch subNet by some method, for example, "docker network inspect kind | jq -r 'map(.IPAM.Config[].Subnet) []'"
2. Calculate the minIP and MaxIP.
3. Fetch all occupied ip list by some method, for example, "docker network inspect kind | jq -r 'map(.Containers[].IPv4Address) []".
4. Loop all IPs between minIP and MaxIP one by one, check if it is occpuied, and return it as long as it is an available one.

Anyway, if you are all fine by current fix, I am also ok with it.

[anusha94]

I feel a little concern about this hard code way, it looks like a potential bug may occurs one day in the future.

I think that’s a very valid concern. We did think about it - but we know we won’t have that many containers now, so this felt a little complex to achieve something so small. Before this PR - we were hardcoding the full IP, see this removed line from Makefile, so compared to that, this PR added some smartness in fetching the subnet and hardcoding only the last octet.
We can revisit this in future if the 151 hardcoding is turning out to be problematic.