Added support for macOS in TestNewHTTPListener

[ws141]

The test TestNewHTTPListener was failing on macOS when running make test

Description

Added a separate string to match remoteAddrErrMsg for macOS.

Motivation and Context

It fixes the test TestNewHTTPListener which was previously failing and giving the following error.

--- FAIL: TestNewHTTPListener (0.00s)
	listener_test.go:238: error: expected = listen tcp 93.184.216.34:9000: bind: cannot assign requested address, got = listen tcp 93.184.216.34:9000: bind: can't assign requested address

How Has This Been Tested?

This was tested by running make test
The tests were ran on macOS 10.12.6 using go 1.8.3.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #4782 into master will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4782      +/-   ##
==========================================
- Coverage   63.56%   63.52%   -0.04%     
==========================================
  Files         188      188              
  Lines       27506    27506              
==========================================
- Hits        17484    17474      -10     
- Misses       8867     8875       +8     
- Partials     1155     1157       +2

Impacted Files	Coverage Δ
cmd/fs-v1-multipart.go	71.94% <0%> (-1.73%)	⬇️
cmd/fs-v1.go	79.06% <0%> (-0.34%)	⬇️
cmd/fs-v1-background-append.go	81.2% <0%> (+2.68%)	⬆️

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