pt-online-schema-change --[no]drop-triggers

From https://bugs.launchpad.net/percona-toolkit/+bug/1209378:

Some users want to rename the tables manually, when the load is low. For this they could use --no-swap-tables but then, the triggers are dropped at the end and the new tables is outdated.

What is the use of --no-swap-tables if the triggers are dropped. If there is a use case, at least an option like "--no-drop-triggers" should be present.

Done in http://bazaar.launchpad.net/~percona-toolkit-dev/percona-toolkit/release-2.2.5/revision/625