Create collection coordinator explicitly wait for majority write concern after creating the shard key index.

The problem is that if the index was already created no write will be performed , in this case the last op time on the current client could be a very old op time, associated with the last write performed by a previous task scheduled on that thead.
In fact the client associated with a thread of the POS pool is instantiated on thread creation and is reused by different tasks.

So the solution would be to properly set the last op time before to wait it to be majority written.