[FIX] forwardport: queue reliability changes

Previous version would break if _process_item itself committed which
was bad

forwardport/models/forwardport.py

@@ -2,8 +2,6 @@
 import logging
 from contextlib import ExitStack
 
-import subprocess
-
 from odoo import fields, models
 
 
@@ -16,12 +14,13 @@ class Queue:
     def _process(self):
         for b in self.search([]):
             try:
-                with self.env.cr.savepoint():
-                    b._process_item()
+                b._process_item()
                 b.unlink()
                 self.env.cr.commit()
             except Exception:
                 _logger.exception("Error while processing %s, skipping", b)
+                self.env.cr.rollback()
+            self.clear_caches()
 
 class BatchQueue(models.Model, Queue):
     _name = 'forwardport.batches'