Change alias behaviour not to create new server section needlessly

[Gregy]

What this PR does / why we need it:
It simplifies alias configuration in nginx template.

Special notes for your reviewer:
I was going through the template code and this section didn't make much sense to me. I would expect it to be defined like in my PR but there could be some reason behind it that I am missing.

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[k8s-reviewable]

This change is 

[coveralls]

Coverage remained the same at 33.492% when pulling e78ad92 on Gregy:optimize-alias into a18daab on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@Gregy thanks!