Fix dereference-symlink value check error

Currently, freezer use a string 'none' to judge if
the parameter 'dereference-symlink' is None or not.
This patch will fix it.

Change-Id: I661debd0b223059824acd8e2b472a6afe1682b09
Closes-Bug: #1691052

freezer/engine/tar/tar_builders.py

@@ -63,7 +63,7 @@ class TarCommandBuilder(object):
             'soft' dereference soft links,
             'hard' dereference hardlinks,
             'all' dereference both.
-            Default 'none'.
+            Default 'None'.
         """
         self.dereference = self.DEREFERENCE_MODE[mode]
 

freezer/job.py

@@ -223,7 +223,7 @@ class BackupJob(Job):
 
                 # Checksum for Backup Consistency
                 if self.conf.consistency_check:
-                    ignorelinks = (self.conf.dereference_symlink == 'none' or
+                    ignorelinks = (self.conf.dereference_symlink is None or
                                    self.conf.dereference_symlink == 'hard')
                     consistency_checksum = checksum.CheckSum(
                         filepath, ignorelinks=ignorelinks).compute()

freezer/tests/commons.py

@@ -286,7 +286,7 @@ class FakeSwiftClient(object):
 
 class BackupOpt1(object):
     def __init__(self):
-        self.dereference_symlink = 'none'
+        self.dereference_symlink = None
         self.mysql_conf = '/tmp/freezer-test-conf-file'
         self.backup_media = 'fs'
         self.lvm_auto_snap = '/dev/null'

specs/job-backup.conf.example

@@ -95,8 +95,8 @@ restart_always_level = False
 dst_file = False
 
 # Follow hard and soft links and archive and dump the
-# files they refer to. Possible options are {none,soft,hard,all}
-dereference_symlink = none
+# files they refer to. Possible options are {None,soft,hard,all}
+dereference_symlink = None
 
 # Set the hostname used to identify the data you want to
 # restore from. If you want to restore data in the same