Fixed issue with tagging of insecure registries.

[NicklasWallgren]

Fixes #2986

[googlebot]

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[googlebot]

CLAs look good, thanks!

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[codecov]

Codecov Report

Merging #3127 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

Impacted Files	Coverage Δ
pkg/skaffold/docker/remote.go	12.96% <0%> (-1.04%)	⬇️