I verified it with virt-viewer-2.0-17.el6.x86_64:
Steps:
1. Prepare a shutdown guest.
2. Run virt-viewer to open the shutdown guest.
$ virt-viewer -c qemu:///system vm1
3. Click "View->Display", Check the "Zoom" and "Displays" item.
4. Click "View->Fullscreen" to make virt-viewer in fullscreen mode, then check the usb icon button in the toolbar.
Results:
After step3, The "Zoom" and "Displays" item are insensitive.
After step4, The usb icon is insensitive.
So move the bug from ON_QA to VERIFIED.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2017-0587.html