transport: pool, closeAll should wait until all connection loops are stopped

[Kulezi]

Right now pool.CloseAll() calls Close() on all connections it has, but doesn't wait until their loops are actually stopped before exiting itself.

Goroutines running the connection loops stop fast, but after session.Close() returns they should be already stopped, otherwise goleak will complain about leaked goroutines in tests.

scylla-go-driver/transport/pool.go

Lines 115 to 122 in 88fc8ef

	// closeAll is called by PoolRefiller.
	func (p *ConnPool) closeAll() {
	for i := range p.conns {
	if conn, ok := p.conns[i].Swap((*Conn)(nil)).(*Conn); ok {
	conn.Close()
	}
	}
	}