ssh: fix format string in client_test.go
ssh: fix format string in client_test.go

Change-Id: I92c3916b0b5628dc2079af82202d9bfef032c708
Reviewed-on: https://go-review.googlesource.com/39430
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Han-Wen Nienhuys <3269a793d567baa2fa5b041e3e5e0a5039790a2f@google.com>

golang/crypto,ScriptRock/crypto,golang/crypto,golang/crypto,ScriptRock/crypto