lxd/api: Show all instance drivers
lxd/api: Show all instance drivers

Closes #7869

Signed-off-by: Alex J Oliver <837960f576b188152575af7fcd4c1b5a1f369bea@gmail.com>

hallyn/lxd,lxc/lxd,hallyn/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,atxwebs/lxd,hallyn/lxd,atxwebs/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,atxwebs/lxd