Make standby promotion reset the recovery pause state to 'not paused'.

Make standby promotion reset the recovery pause state to 'not paused'.

If a promotion is triggered while recovery is paused, the paused state ends
and promotion continues. But previously in that case
pg_get_wal_replay_pause_state() returned 'paused' wrongly while a promotion
was ongoing.

This commit changes a standby promotion so that it marks the recovery
pause state as 'not paused' when it's triggered, to fix the issue.

Author: Fujii Masao
Reviewed-by: Dilip Kumar, Kyotaro Horiguchi
Discussion: https://postgr.es/m/f706876c-4894-0ba5-6f4d-79803eeea21b@oss.nttdata.com