Reset 'ps' display just once when resolving VXID conflicts.

Reset 'ps' display just once when resolving VXID conflicts.

This prevents the word "waiting" from briefly disappearing from the ps
status line when ResolveRecoveryConflictWithVirtualXIDs begins a new
iteration of the outer loop.

Along the way, remove some useless pgstat_report_waiting() calls;
the startup process doesn't appear in pg_stat_activity.

Fujii Masao