After the logical replication launcher was told to wake up at
commit (for example, by a CREATE SUBSCRIPTION command), the flag to wake
up was not reset, so it would be woken up at every following commit as
well.  So fix that by resetting the flag.

Also, we don't need to wake up anything if the transaction was rolled
back.  Just reset the flag in that case.

Author: Masahiko Sawada <sawada.mshk@gmail.com>
Reported-by: Fujii Masao <masao.fujii@gmail.com>