Clarify that spawning network in k8s should be in default namespace

[Neyromancer]

Description

While trying to spawn a network in kubernetes an error occures when namesapce is set to a value different from default:

Error:  	 Error: Command failed with exit code 1: kubectl --kubeconfig /Users/wirednkod/.kube/config apply -f -
Error from server (NotFound): error when creating "STDIN": namespaces "zombie-b3b08c66fc8e8e48d2876049d4477f7e" not found
Error from server (NotFound): error when creating "STDIN": namespaces "zombie-b3b08c66fc8e8e48d2876049d4477f7e" not found
Error from server (NotFound): error when creating "STDIN": namespaces "zombie-b3b08c66fc8e8e48d2876049d4477f7e" not found
Error from server (NotFound): error when creating "STDIN": namespaces "zombie-b3b08c66fc8e8e48d2876049d4477f7e" not found

Related Issue #1412 Error when trying to spawn network in kubernetes

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Tasks:

• [ ] Make clear in the docs that you need to be set in the default namespace to start working with zombienet.
• [ ] Print a warning at start that different then default namspace is used
• [ ] Code review
• [ ] Test

[cla-bot-2021[bot]]

User @Neyromancer, please sign the CLA here.

[wirednkod]

@Neyromancer Thank you for the contributions. Just a reminder that docs will automatically update so there is no need to manual edit them

[Neyromancer]

i am also going to add logs with current namespace

[wirednkod]

@Neyromancer is this ready for review? @pepoviola if this looks fine - I think we can merge it. What do you think?

[pepoviola]

ping @Neyromancer are you still working on this? Thx!