Bug 796120

escription of problem:
Add a new VLAN,change the VLAN tag from 0 to 1 manually,select the eth0 as parent interface,and then click finish,it will fail.

Version-Release number of selected component (if applicable):
libvirt-0.9.10-2.el6.x86_64
virt-manager-0.9.0-10.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1.Open virt-manager
#virt-manager --debug
2.Click Edit->Connection Details,click Network Interfaces tab.
3. Click + button
4.Select interface type as 'VLAN', click Forward button.
5 Select start mode as 'none', enable "Activate now", fill VLAN tag as 1(The default value is 0) manually,do not use the arrows.

6.And then,choose eth0 as parent interface. Click Finish button.


Actual results:
1.After choose eth0 as parent interface,the "Name" of VLAN don't 
synchronize with VLAN tag 1, still is eth0.0.
2.After click "Finish" ;
"Error creating interface: 'Could not create interface: Interface not 
found: couldn't find interface named 'eth0.0'' pop up.
3.Close the Error diaglog,and then click "cancel".
The eth0.1 was created, but with Inactive status.

Expected results:
1. The VLAN name need to synchronize with VLAN tag 1,update to eth0.1


Additional info:
1.At step 5,must enable "Activate now".
2.At step 6,if check 'eth0' -> uncheck 'eth0' -> check 'eth0',the Name 
will change to 'eth0.1',then click Finish,it will create successfully.