Fix unnecessary retrying when the link is down in dhcp.

From the dhcp daemon log, we can see that dhcp will fail to acquire
the lease when the link is down, and success on retry.

```
2024/08/21 21:30:44 macvlan-dhcp/eth1: acquiring lease
2024/08/21 21:30:44 Link "eth1" down. Attempting to set up
2024/08/21 21:30:44 network is down
2024/08/21 21:30:44 retrying in 2.641696 seconds
2024/08/21 21:30:49 macvlan-dhcp/eth1: lease acquired, expiration is 2024-08-22 09:30:49.755367962 +0800 CST m=+43205.712107889
```

After move the code of set up link to the beginning of the function, the
dhcp success on first time.

```
2024/08/21 22:04:02 macvlan-dhcp/eth1: acquiring lease
2024/08/21 22:04:02 Link "eth1" down. Attempting to set up
2024/08/21 22:04:05 macvlan-dhcp/eth1: lease acquired, expiration is 2024-08-22 10:04:05.297887726 +0800 CST m=+43203.081141304
```

Signed-off-by: Songmin Li <lisongmin@protonmail.com>

plugins/ipam/dhcp/lease.go

@@ -234,19 +234,19 @@ func (l *DHCPLease) getAllOptions() dhcp4.Options {
 }
 
 func (l *DHCPLease) acquire() error {
-	c, err := newDHCPClient(l.link, l.timeout, l.broadcast)
-	if err != nil {
-		return err
-	}
-	defer c.Close()
-
 	if (l.link.Attrs().Flags & net.FlagUp) != net.FlagUp {
 		log.Printf("Link %q down. Attempting to set up", l.link.Attrs().Name)
-		if err = netlink.LinkSetUp(l.link); err != nil {
+		if err := netlink.LinkSetUp(l.link); err != nil {
 			return err
 		}
 	}
 
+	c, err := newDHCPClient(l.link, l.timeout, l.broadcast)
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+
 	opts := l.getAllOptions()
 
 	pkt, err := backoffRetry(l.resendMax, func() (*dhcp4.Packet, error) {