Problem: Resume after interrupted clone always fails (#698)

We always call `summary_start_timing` regardless of whether the section has been already done or not., which causing insertion(insert or replace) of default value to `done_time_epoch` because `summary_start_timing` won't be called for already done section.

Solution: Check whether the section is already completed using `runState` and exit early without calling `summary_start_timing` for already done section.

Related to https://github.com/dimitri/pgcopydb/issues/692



Signed-off-by: Arunprasad Rajkumar <ar.arunprasad@gmail.com>