fixed race condition for parallel use case

[lamchakchan]

Description

• There was a bug when any of the methods that leveraged _autoConnectChannel was invoked in a parallel fashion raising a race condition on side to side instantiations of TCP connections. A semaphore is put in place to prevent this.

Related Issue

• Possible issue with race condition  #53

Motivation and Context

Bug

Types of changes

• Documentation only (no changes to either lib/ or test/ files)
• Bug fix (non-breaking change which fixes an issue. you didn't modify existing tests)
• New feature (non-breaking change which adds functionality. you added at least one new test)
• Breaking change (fix or feature that would cause existing functionality to change. you had to modify existing tests.)

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the Hapi.js style guide.
• I have updated the documentation as needed.
• I have added tests to cover my changes.
• All new and existing tests passed.