tests: clarify which process seems to be leaking fds

The tests check if they leak fds themselves, but we also
check if gocryptfs leaks fds. Clarify what is what in the
error message.

tests/cli/cli_test.go

@@ -26,7 +26,7 @@ func TestMain(m *testing.M) {
 	r := m.Run()
 	after := test_helpers.ListFds(0)
 	if len(before) != len(after) {
-		fmt.Printf("fd leak? before, after:\n%v\n%v\n", before, after)
+		fmt.Printf("fd leak in test process? before, after:\n%v\n%v\n", before, after)
 		os.Exit(1)
 	}
 	os.Exit(r)

tests/matrix/matrix_test.go

@@ -83,7 +83,7 @@ func TestMain(m *testing.M) {
 		// the gocryptfs FUSE process, but only in the tests that access it!
 		after := test_helpers.ListFds(0)
 		if len(before) != len(after) {
-			fmt.Printf("fd leak? before, after:\n%v\n%v\n", before, after)
+			fmt.Printf("fd leak in test process? before, after:\n%v\n%v\n", before, after)
 			os.Exit(1)
 		}
 		test_helpers.UnmountPanic(test_helpers.DefaultPlainDir)

tests/test_helpers/mount_unmount.go

@@ -175,7 +175,7 @@ func UnmountErr(dir string) (err error) {
 		err = cmd.Run()
 		if err == nil {
 			if len(fdsNow) > len(fds)+maxCacheFds {
-				return fmt.Errorf("FD leak? pid=%d dir=%q, fds:\nold=%v \nnew=%v\n", pid, dir, fds, fdsNow)
+				return fmt.Errorf("fd leak in gocryptfs process? pid=%d dir=%q, fds:\nold=%v \nnew=%v\n", pid, dir, fds, fdsNow)
 			}
 			return nil
 		}