journald: Fix action comment and use --vacuum-size=0

`--vacuum-*` commands only remove archived log files, so need to
investigate how to forcefullty archive them.

Also need to sum up sizes from all files removed instead of using
only the last one.

bleachbit/Action.py

@@ -466,15 +466,15 @@ def get_commands(self):
 
 
 class Journald(ActionProvider):
-    """Action to run 'journalctl --vacuum-time=1'"""
+    """Action to run 'journalctl --vacuum-size=0'"""
     action_key = 'journald.clean'
 
     def __init__(self, action_element, path_vars=None):
         ActionProvider.__init__(self, action_element, path_vars)
 
     def get_commands(self):
         if FileUtilities.exe_exists('journalctl'):
-            yield Command.Function(None, Unix.journald_clean, 'journalctl --vacuum-time=1')
+            yield Command.Function(None, Unix.journald_clean, 'journalctl --vacuum-size=0')
 
 
 class Json(FileActionProvider):

bleachbit/Unix.py

@@ -605,7 +605,7 @@ def run_cleaner_cmd(cmd, args, freed_space_regex=r'[\d.]+[kMGTE]?B?', error_line
 def journald_clean():
     """Clean the system journals"""
     try:
-        return run_cleaner_cmd('journalctl', ['--vacuum-size=1'], JOURNALD_REGEX)
+        return run_cleaner_cmd('journalctl', ['--vacuum-size=0'], JOURNALD_REGEX)
     except subprocess.CalledProcessError as e:
         raise RuntimeError("Error calling '%s':\n%s" %
                            (' '.join(e.cmd), e.output))