Do not print the manifest on to stdout when doing a deploy by kustomize

[RaviTezu]

Fixes #1231

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[codecov-io]

Codecov Report

Merging #1234 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1234      +/-   ##
==========================================
+ Coverage   41.45%   41.47%   +0.01%     
==========================================
  Files          96       96              
  Lines        4238     4236       -2     
==========================================
  Hits         1757     1757              
+ Misses       2310     2308       -2     
  Partials      171      171

Impacted Files	Coverage Δ
pkg/skaffold/deploy/kustomize.go	35.71% <ø> (+0.99%)	⬆️

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[googlebot]

CLAs look good, thanks!

[dgageot]

LGTM