Use FQCN to prevent classloader issues on java6

Motivation:

We need to use FQCN to prevent classloader issues for classes that are > Java6. This is a cleanup of ed5fcbb.

Modifications:

Just remove the imports and use FQCN.

Result:

No classloader issues with java6

common/src/main/java/io/netty/util/internal/NativeLibraryLoader.java

@@ -27,8 +27,6 @@
 import java.io.OutputStream;
 import java.lang.reflect.Method;
 import java.net.URL;
-import java.nio.file.Files;
-import java.nio.file.attribute.PosixFilePermission;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.Arrays;
@@ -409,17 +407,20 @@ private static boolean canExecuteExecutable(File file) throws IOException {
             // the UnixFileStore, though the flag is not exposed via a public API.  To find out if library is being
             // loaded off a volume with noexec, confirm or add executalbe permissions, then check File#canExecute().
 
-            Set<PosixFilePermission> existingFilePermissions = Files.getPosixFilePermissions(file.toPath());
-            Set<PosixFilePermission> executePermissions = EnumSet.of(PosixFilePermission.OWNER_EXECUTE,
-                                                                     PosixFilePermission.GROUP_EXECUTE,
-                                                                     PosixFilePermission.OTHERS_EXECUTE);
+            // Note: We use FQCN to not break when netty is used in java6
+            Set<java.nio.file.attribute.PosixFilePermission> existingFilePermissions =
+                    java.nio.file.Files.getPosixFilePermissions(file.toPath());
+            Set<java.nio.file.attribute.PosixFilePermission> executePermissions =
+                    EnumSet.of(java.nio.file.attribute.PosixFilePermission.OWNER_EXECUTE,
+                            java.nio.file.attribute.PosixFilePermission.GROUP_EXECUTE,
+                            java.nio.file.attribute.PosixFilePermission.OTHERS_EXECUTE);
             if (existingFilePermissions.containsAll(executePermissions)) {
                 return false;
             }
 
-            Set<PosixFilePermission> newPermissions = EnumSet.copyOf(existingFilePermissions);
+            Set<java.nio.file.attribute.PosixFilePermission> newPermissions = EnumSet.copyOf(existingFilePermissions);
             newPermissions.addAll(executePermissions);
-            Files.setPosixFilePermissions(file.toPath(), newPermissions);
+            java.nio.file.Files.setPosixFilePermissions(file.toPath(), newPermissions);
             return file.canExecute();
         }