lxd/instance/drivers/qmp/commands: Improve comment on SendFile to aid searchability
lxd/instance/drivers/qmp/commands: Improve comment on SendFile to aid searchability

For a function that sends a file descriptor it aids finding it if the description includes the words "file descriptior".

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

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