Remove hardcoded reference to "localhost"

[iamsamirzon]

Created from #93 to fix hardcoded references to "localhost" to also include 127.0.0.1. Refer one example here. #83 (comment) .

Desired Resolution

• Address all hardcoded references to "localhost" by doing a search through all Notation repos.

[dtzar]

Doing a search on notation repo, there are only two references:

1. notation/cmd/notation/registry.go

   Line 5 in 1356216

   "net"

2. notation/pkg/configutil/docker_config_test.go

   Line 13 in 1356216

   "localhost:5000": "pass"

2 - is in a test, so likely don't need to replace.

[shizhMSFT]

The original comment is to refactor the following code to a function:

notation/cmd/notation/registry.go

Line 54 in 4bf25df

if host, _, _ := net.SplitHostPort(ref.Registry); host == "localhost" {

[priteshbandi]

Discuss with Yi and probably close it if the work is already done

[yizha1]

The problem still exists. Let's address it in rc.2