fix auto-update

plugin_installer/manifest.ini

 [info]
 name: Plugin Installer
 short_name: plugin_installer
-version: 0.9.3
+version: 0.10.0
 description: Install and upgrade plugins from ftp
 authors: Denis Fomin <fominde@gmail.com>
  Yann Leboulanger <asterix@lagaule.org>

plugin_installer/plugin_installer.py

@@ -109,7 +109,7 @@ class PluginInstaller(GajimPlugin):
                 to_update = []
                 con = self.ftp_connect()
                 con.cwd('plugins')
-                self.ftp.retrbinary('RETR manifests.zip', ftp.handleDownload)
+                con.retrbinary('RETR manifests.zip', ftp.handleDownload)
                 zip_file = zipfile.ZipFile(ftp.buffer_)
                 manifest_list = zip_file.namelist()
                 for filename in manifest_list: