Fix dbapi to support "Abandon Changes & Quit" feature

Fixes #11599

gramps/gen/db/generic.py

@@ -535,7 +535,7 @@ class DbGeneric(DbWriteBase, DbReadBase, UpdateCallback, Callback):
         self.undo_history_callback = None
         self.modified = 0
         self.transaction = None
-        self.abort_possible = False
+        self.abort_possible = True
         self._bm_changes = 0
         self.has_changed = False
         self.surname_list = []

gramps/plugins/db/dbapi/dbapi.py

@@ -231,6 +231,10 @@ class DBAPI(DbGeneric):
         _LOG.debug("    %sDBAPI %s transaction begin for '%s'",
                    "Batch " if transaction.batch else "",
                    hex(id(self)), transaction.get_description())
+        if transaction.batch:
+            # A batch transaction does not store the commits
+            # Aborting the session completely will become impossible.
+            self.abort_possible = False
         self.transaction = transaction
         self.dbapi.begin()
         return transaction