Ensure all IPv4 addresses use only 4 bytes.

[pboothe]

Also, convert the -eventsocket flag to the one provided in tcpinfo.eventsocket

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 151

• 17 of 17 (100.0%) changed or added relevant lines in 3 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 142:	0.0%
Covered Lines:	515
Relevant Lines:	515

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💛 - Coveralls

[stephen-soltesz]

Reviewed 4 of 5 files at r1.
Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @pboothe and @stephen-soltesz)

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tcpinfohandler/handler.go, line 42 at r1 (raw file):

		return
	}
	if srcIP.To4() != nil {

Please add a comment regarding why this is necessary.

If this logic through the creation of the UUIDEvent below were in a small helper function that helper could be tested pretty easily.

[stephen-soltesz]

Reviewed 1 of 5 files at r1.
Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @pboothe and @stephen-soltesz)

[stephen-soltesz]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @pboothe)

[stephen-soltesz]

https://github.com/m-lab/dev-tracker/issues/442