Fix trivial style errors reported by go vet and golint

No substantial code change.
Note that some style errors reported by `golint` are not fixed due to possible compatibility issues.

Signed-off-by: Akihiro Suda <suda.kyoto@gmail.com>

libcontainer/keys/keyctl.go

@@ -4,9 +4,9 @@ package keyctl
 
 import (
 	"fmt"
-	"syscall"
-	"strings"
 	"strconv"
+	"strings"
+	"syscall"
 	"unsafe"
 )
 
@@ -17,7 +17,7 @@ const KEYCTL_DESCRIBE = 6
 type KeySerial uint32
 
 func JoinSessionKeyring(name string) (KeySerial, error) {
-	var _name *byte = nil
+	var _name *byte
 	var err error
 
 	if len(name) > 0 {
@@ -34,7 +34,7 @@ func JoinSessionKeyring(name string) (KeySerial, error) {
 	return KeySerial(sessKeyId), nil
 }
 
-// modify permissions on a keyring by reading the current permissions,
+// ModKeyringPerm modifies permissions on a keyring by reading the current permissions,
 // anding the bits with the given mask (clearing permissions) and setting
 // additional permission bits
 func ModKeyringPerm(ringId KeySerial, mask, setbits uint32) error {
@@ -64,4 +64,3 @@ func ModKeyringPerm(ringId KeySerial, mask, setbits uint32) error {
 
 	return nil
 }
-