net/rpc/jsonrpc: add temporarily-disabled failing test
net/rpc/jsonrpc: add temporarily-disabled failing test

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Update Issue 7442

LGTM=adg
R=adg
CC=golang-codereviews
https://codereview.appspot.com/69860056

pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme