all: fix ineffectual assignments

audited using ineffassign tool from
github.com/gordonklaus/ineffassign
go generate does not generate any changes

Change-Id: Iabbec9ec1aae39081289d503d79fd7b4caadf17b
GitHub-Last-Rev: acd17cce410e9c68ce3c87b5546261be9153e3ea
GitHub-Pull-Request: golang/crypto#70
Reviewed-on: https://go-review.googlesource.com/c/155942
Reviewed-by: Filippo Valsorda <filippo@golang.org>

ssh/benchmark_test.go

@@ -93,6 +93,9 @@ func BenchmarkEndToEnd(b *testing.B) {
 			b.Fatalf("Client: %v", err)
 		}
 		ch, incoming, err := newCh.Accept()
+		if err != nil {
+			b.Fatalf("Accept: %v", err)
+		}
 		go DiscardRequests(incoming)
 		for i := 0; i < b.N; i++ {
 			if _, err := io.ReadFull(ch, output); err != nil {