Recovery API should also report ongoing relocation recoveries

We currently only report relocation related recoveries after they are done.

Closes #6585
[Test] add awaitFix to rerouteRecoveryTest
[Test] improved recovery slow down in rerouteRecoveryTest

only change recovery throttling to slow down recoveries. The recovery file chunk size updates are not picked up by ongoing recoveries. That cause the recovery to take too long even after the default settings are restored.

Also - change document creation to reuse field names in order to speed up the test.