Add sockid to Close

[gfr10598]

tcp-info is already caching the SockID for connections, so should send it with the Close events, instead of requiring clients to cache it too.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 918

• 11 of 13 (84.62%) changed or added relevant lines in 4 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.2%) to 82.748%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
inetdiag/structs.go	2	3	66.67%
saver/saver.go	2	3	66.67%
<!--	Total:	11	13

Files with Coverage Reduction	New Missed Lines	%
inetdiag/structs.go	1	95.69%
saver/saver.go	1	75.3%
<!--	Total:	2

Totals
Change from base Build 911:	-0.2%
Covered Lines:	1084
Relevant Lines:	1310

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💛 - Coveralls