oc: remove and disable userContext after each call

This adds [MAPIStoreUserContext activate] method to use
it instead of activateWithUser.

A cleanup operation is executed after each public function
so there won't be any conflicts with future calls.

In practice, this will deactivate the current user context set on
MAPIApp, this means two things: (1) set nil as current user context
on MAPIApp and (2) remove woContext from current thread dictionary

OpenChange/MAPIStoreSOGo.m

@@ -74,10 +74,12 @@ static BOOL initialization_done = NO;
 #define TRYCATCH_END(pool)  \
           } @catch (NSException * e) { \
             enum mapistore_error ret = sogo_backend_handle_objc_exception(e, __PRETTY_FUNCTION__, __LINE__); \
+            mapiapp_cleanup(); \
             [pool release]; \
             NS_CURRENT_THREAD_TRY_UNREGISTER(); \
             return ret; \
-          }
+          } \
+        mapiapp_cleanup();
 
 
 static enum mapistore_error
@@ -199,12 +201,28 @@ sogo_backend_init (void)
   return MAPISTORE_SUCCESS;
 }
 
+/**
+   \details Cleanup operation to execute after an action has been performed
+   so there won't be any conflicts with future calls.
+   In practice this will deactivate the current user context set on MAPIApp
+   (which is the current WOApplication), this means two things: (1) set nil
+   as current user context on MAPIApp and (2) remove woContext from current
+   thread dictionary (this is used on WOContext.m).
+*/
+static void mapiapp_cleanup(void)
+{
+  Class MAPIApplicationK;
+  MAPIApplicationK = NSClassFromString (@"MAPIApplication");
+  if (MAPIApplicationK)
+    [[MAPIApplicationK application] cleanup];
+}
+
 /**
    \details Create a connection context to the sogo backend
 
    \param mem_ctx pointer to the memory context
    \param uri pointer to the sogo path
-   \param private_data pointer to the private backend context 
+   \param private_data pointer to the private backend context
 */
 
 static enum mapistore_error