doc/security: edit information about name leakage
doc/security: edit information about name leakage

Update and edit the information about preventing name leakage of
instances.

Signed-off-by: Ruth Fuchss <90c286bb8b7c8291b9f5a2a1d38dc233728381fe@canonical.com>

stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,stgraber/lxd