slapproxy: Fix migration of forwarded requests

When migrating entries, use `INSERT OR REPLACE` to get rid of duplicate
rows that cause constraint violations, instead of raising an exception.

Note that this only affects the `forwarded_partition_request` table:
for other tables it changes nothing in terms of behavior because the
intial tables already cannot contain conflicting rows.

slapos/proxy/views.py

@@ -194,7 +194,7 @@ def _upgradeDatabaseIfNeeded():
     for row in execute_db(table, 'SELECT * from %s', db_version=current_schema_version):
       columns = ', '.join(row.keys())
       placeholders = ':'+', :'.join(row.keys())
-      query = 'INSERT INTO %s (%s) VALUES (%s)' % ('%s', columns, placeholders)
+      query = 'INSERT OR REPLACE INTO %s (%s) VALUES (%s)' % ('%s', columns, placeholders)
       execute_db(table, query, row)
   # then drop old tables
   for previous_table in previous_table_list: