Add postUnmount plugin callback

This is useful for unmounting the remote drive over ssh after sshfs
is unmounted.

If the remote drive is unmounted before sshfs with the existing callback,
then sshfs can not be unmounted and the mountpoint shows up as
d????????? ? ?         ?            ?            ? mountpoint
until the remote drive is remounted.

common/mount.py

@@ -176,6 +176,7 @@ def umount(self, hash_id = None):
                                  parent = self.parent,
                                  **kwargs)
             backend.umount()
+        self.config.PLUGIN_MANAGER.postUnmount(self.profile_id)
 
     def preMountCheck(self, mode = None, first_run = False, **kwargs):
         """

common/pluginmanager.py

@@ -65,6 +65,9 @@ def mount(self, profileID = None):
     def unmount(self, profileID = None):
         return
 
+    def postUnmount(self, profileID = None):
+        return
+
 class PluginManager:
     def __init__(self):
         self.plugins = []
@@ -180,6 +183,13 @@ def unmount(self, profileID = None):
             except BaseException as e:
                 self.logError(plugin, e)
 
+    def postUnmount(self, profileID = None):
+        for plugin in reversed(self.plugins):
+            try:
+                plugin.postUnmount(profileID)
+            except BaseException as e:
+                self.logError(plugin, e)
+
     def logError(self, plugin, e):
         logger.error('Plugin %s %s failed: %s'
                      %(plugin.__module__,               #plugin name

common/plugins/usercallbackplugin.py

@@ -90,3 +90,6 @@ def mount(self, profileID = None):
 
     def unmount(self, profileID = None):
         self.callback('8', profileID = profileID)
+
+    def postUnmount(self, profileID = None):
+        self.callback('9', profileID = profileID)