have you tried a different connection URI?:

--------------<-----------------
$ virsh -c qemu:///system 'list'
-------------->-----------------

If not explicitly stated, the virsh binary uses the 'qemu:///session' URI
(at least under debian).

See also .. VIRSH(1):

----------------------------------<---------------------------------------
qemu:///system
"connect locally as root to the daemon supervising QEmu and KVM domains"

qemu:///session
"connect locally as a normal user to his own set of QEmu and KVM domains"
---------------------------------->---------------------------------------

Please note that in order for the 'qemu:///system' URI to work probably the
user must be part of the 'libvirt' group. This way you won't have to touch
the permission set of any of the respective sockets.