test commit_delay

I am trying to see the impact of commit_delay.

Set it to 100000 (microseconds), i.e. to 100ms

synchronous_commit is kept to default (i.e. ON)

Now I expect my DML statements to take atleast 100ms. But when I try to execute a few and measure using the timing command of postgres or the time command of linux, the duration is just a few milliseconds.