Adds public IP of LB to localIPs slice

[nkinkade]

Virtual machines will be part of managed instance groups, which sit behind a pass-through TCP load balancer. In such cases, packets arriving to the machine from the load balancer will have a destination address of the load balancer's public IP, which is not a local address on the machine. Without these changes uuid-annotator will refuse to annoate a connection, since it doesn't recognize either the Src of Dest IP address as being its own (annotate.FindDirection() fails). These changes cause siteannotator.New() to append the public IP address from siteinfo to localIPs if it is a virtual machine.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 303

• 27 of 27 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 298:	0.0%
Covered Lines:	773
Relevant Lines:	773

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💛 - Coveralls