vspd: Stop scanning when ticket spender found.

Once the spender of a given ticket is found, the rest of the blocks
don't need to be checked.

cmd/vspd/spentticket.go

@@ -172,6 +172,9 @@ func (v *vspd) findSpentTickets(toCheck database.TicketList, startHeight int64)
 				// Current index has been removed which means everything else
 				// moved up one and thus the same index needs to be repeated.
 				i--
+
+				// Check next ticket.
+				break
 			}
 		}