Update messages are logged in the wrong order

[pfrenssen]

Partially fixes #3296.

When performing multiple database updates in a row, the individual messages that are returned by the update hooks are output in the log after all the updates have finished. This might give the impression that the updates have been performed in parallel or out of order, and this might be misleading for system administrators that are investigating a failed update.

Currently the output might look like this:

 [notice] Executing woot_update_8101
 [ok] Performing woot_update_8101
 [notice] Executing woot_update_8102
 [error]  8102 error 
 [ok] Performing woot_update_8102
 [notice] woot_update_8101 <----- out of order
 [error]  Failed batch process: woot_update_8102 
 [error]  Finished performing updates. 

[pfrenssen]

The test shows that the update message is displayed out of order. Now let's fix it.

[claudiu-cristea]

Discussed with @pfrenssen and I will review this PR tomorrow morning so it can be quickly ready for the 9 stable release.

[claudiu-cristea]

I rerolled the PR. Tested on a big project with a lot of updates. The order of log messages is OK. We have also tests, what else. @weitzman, +1 for merging.

[weitzman]

Merged by #3310