Fix inconsistent doc string and code of db_sync

db_sync may downgrade but current doc string only says
upgrade, and it says having return value which seems not
true.

Change-Id: Ib7bbb597f621985aba956302034eb1c5d0b3ff1f
Closes-Bug: #1264193
Fix the incorrect log message when creating images

When using "nova image-create my_server_id name" to create an image, the
glance api log image id is incorrect in the method create().

Change-Id: I938279526ed5adf5b95ec5f67e78c6465f890898
Closes-bug: #1263647
Merge "Fix the incorrect log message when creating images"
Merge "Fix inconsistent doc string and code of db_sync"