Fix errors caught by go vet in compliance package

`go test` implicitly runs `go vet` and fails the tests if vet
errors are found.  Fix all the issues found by vet.

Test: go test build/make/tools/compliance/...
Change-Id: If0684cf124ece4931af440008cd44a61c22de475
diff --git a/tools/compliance/cmd/dumpgraph_test.go b/tools/compliance/cmd/dumpgraph_test.go
index 3055022..6555aab 100644
--- a/tools/compliance/cmd/dumpgraph_test.go
+++ b/tools/compliance/cmd/dumpgraph_test.go
@@ -1217,7 +1217,7 @@
 			outList := strings.Split(stdout.String(), "\n")
 			outLine := 0
 			if outList[outLine] != "strict digraph {" {
-				t.Errorf("dumpgraph: got 1st line %v, want strict digraph {")
+				t.Errorf("dumpgraph: got 1st line %v, want strict digraph {", outList[outLine])
 			}
 			outLine++
 			if strings.HasPrefix(strings.TrimLeft(outList[outLine], " \t"), "rankdir") {