net: make network client name unique

assign_name() creates a name MODEL.NUM, where MODEL is the client's model,
and NUM is the number of MODELs that already exist.

Markus added NIC naming for non-VLAN clients in commit 53e51d85.
commit d33d93b2 incorrectly added a judgement of net-hub. It caused
net clients created with -netdev get same names.

eg:
 # qemu-upstream -device virtio-net-pci,netdev=h1 -netdev tap,id=h1 \
                    -device virtio-net-pci,netdev=h2 -netdev tap,id=h2 ..
 (qemu) info network
 virtio-net-pci.0: index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
  \ h1: index=0,type=tap,ifname=tap0,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
 virtio-net-pci.0: index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:57
  \ h2: index=0,type=tap,ifname=tap1,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown

This patch removed the check of nic-hub, and created unique names for
all net clients that have same model.

v2: update commitlog & comments
Signed-off-by: NAmos Kong <akong@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

net/net.c

@@ -157,8 +157,7 @@ void qemu_macaddr_default_if_unset(MACAddr *macaddr)
 /**
  * Generate a name for net client
  *
- * Only net clients created with the legacy -net option need this.  Naming is
- * mandatory for net clients created with -netdev.
+ * Only net clients created with the legacy -net option and NICs need this.
  */
 static char *assign_name(NetClientState *nc1, const char *model)
 {
@@ -170,9 +169,7 @@ static char *assign_name(NetClientState *nc1, const char *model)
         if (nc == nc1) {
             continue;
         }
-        /* For compatibility only bump id for net clients on a vlan */
-        if (strcmp(nc->model, model) == 0 &&
-            net_hub_id_for_client(nc, NULL) == 0) {
+        if (strcmp(nc->model, model) == 0) {
             id++;
         }
     }