Fix issues found by ineffassign

gocryptfs$ ineffassign ./...

/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/configfile/config_file.go:243:2: ineffectual assignment to scryptHash
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/configfile/config_file.go:272:2: ineffectual assignment to scryptHash
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/file.go:285:3: ineffectual assignment to fileID
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/node.go:367:3: ineffectual assignment to err
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/node_open_create.go:68:2: ineffectual assignment to fd
/home/jakob/go/src/github.com/rfjakob/gocryptfs/mount.go:308:2: ineffectual assignment to masterkey
/home/jakob/go/src/github.com/rfjakob/gocryptfs/gocryptfs-xray/xray_main.go:156:13: ineffectual assignment to err
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/prepare_syscall_test.go:65:16: ineffectual assignment to errno
/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/syscallcompat/open_nofollow_test.go:34:2: ineffectual assignment to fd
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/defaults/acl_test.go:111:6: ineffectual assignment to err
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/defaults/acl_test.go:181:2: ineffectual assignment to sz
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/defaults/acl_test.go:198:2: ineffectual assignment to sz
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/defaults/main_test.go:365:8: ineffectual assignment to err
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/xattr/xattr_fd_test.go:30:6: ineffectual assignment to err
/home/jakob/go/src/github.com/rfjakob/gocryptfs/tests/xattr/xattr_fd_test.go:66:6: ineffectual assignment to err

3 files changed, 14 insertions, 4 deletions

diff --git a/tests/defaults/acl_test.go b/tests/defaults/acl_test.go
index b3826e8..f3c707e 100644
--- a/tests/defaults/acl_test.go
+++ b/tests/defaults/acl_test.go
@@ -109,6 +109,9 @@ func TestAcl543(t *testing.T) {
 		t.Fatal(err)
 	}
 	fi, err := os.Stat(fn1)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if fi.Mode() != modeWant {
 		t.Fatalf("mode changed from %o to %o", modeWant, fi.Mode())
 	}
@@ -178,7 +181,7 @@ func TestXattrOverflow(t *testing.T) {
 	if sz != len(val) {
 		t.Errorf("wrong sz: want %d have %d", len(val), sz)
 	}
-	sz, err = unix.Lgetxattr(fn, attr, make([]byte, 1))
+	_, err = unix.Lgetxattr(fn, attr, make([]byte, 1))
 	if err != syscall.ERANGE {
 		t.Error(err)
 	}
@@ -195,7 +198,7 @@ func TestXattrOverflow(t *testing.T) {
 	if sz != szWant {
 		t.Errorf("wrong sz: want %d have %d", szWant, sz)
 	}
-	sz, err = unix.Llistxattr(fn, make([]byte, 1))
+	_, err = unix.Llistxattr(fn, make([]byte, 1))
 	if err != syscall.ERANGE {
 		t.Error(err)
 	}
diff --git a/tests/defaults/main_test.go b/tests/defaults/main_test.go
index 2513860..ddaca68 100644
--- a/tests/defaults/main_test.go
+++ b/tests/defaults/main_test.go
@@ -363,6 +363,9 @@ func TestMd5sumMaintainers(t *testing.T) {
 
 	cmd := exec.Command("md5sum", fn, fn, fn, fn)
 	out2, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatal(err)
+	}
 	out := string(out2)
 
 	// 195191 zero bytes have this md5sum
diff --git a/tests/xattr/xattr_fd_test.go b/tests/xattr/xattr_fd_test.go
index d3f02c5..7415e54 100644
--- a/tests/xattr/xattr_fd_test.go
+++ b/tests/xattr/xattr_fd_test.go
@@ -28,7 +28,9 @@ func TestFdXattr(t *testing.T) {
 	defer syscall.Close(fd)
 	buf := make([]byte, 1000)
 	sz, err := unix.Flistxattr(fd, buf)
-	if sz != 0 {
+	if err != nil {
+		t.Error(err)
+	} else if sz != 0 {
 		t.Errorf("expected zero size, got %d", sz)
 	}
 	val1 := []byte("123456789")
@@ -64,7 +66,9 @@ func TestFdXattr(t *testing.T) {
 		t.Error(err)
 	}
 	sz, err = unix.Flistxattr(fd, buf)
-	if sz != 0 {
+	if err != nil {
+		t.Error(err)
+	} else if sz != 0 {
 		t.Errorf("expected zero size, got %d", sz)
 	}
 }