Add upstream parameters in nginx-asg-sync

[bvighnesha]

Proposed changes

As a user, I would like to configure upstream server parameters for both http and stream upstreams.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork

[Rulox]

Thanks.

Looks good, I have added a few comments/suggestions.

Additionally, we need to add documentation of the new fields here:
https://github.com/nginxinc/nginx-asg-sync/blob/master/examples/aws.md

and here:
https://github.com/nginxinc/nginx-asg-sync/blob/master/examples/azure.md

[Rulox]

Hi @b-v-r sorry I missed one thing about max_fails last time I reviewed it, but I think is important we take care of.

Also I suggest to add default values in docs (check my suggestion). Thanks again!

[Rulox]

Looks better now thanks!

PS: This PR can't be merged until we update the UpdateHTTP method of the go client. Right now it does not perform updates on the Upstream parameters.

[Dean-Coakley]

Looks good, just some small comments regarding test style/consistency and structure.

[Dean-Coakley]

The leading spaces in cmd/sync/main_test.go still look strange to me.
For example:
t.Errorf(" setPositiveInt() -> t.Errorf("setPositiveInt()

Aside from that, this looks ready. - Just need updated UpdateHTTP method from go client to proceed.

[Rulox]

Closing in favour of #33