Update design doc of node security
Update design doc of node security

This patch updates the design doc of Ganeti's node
security. It turned out that the solution of freezing
master capability is not feasible. This patch explains
the reasons and the alternative considered.

Signed-off-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>
Reviewed-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>

mbakke/ganeti,ganeti/ganeti,andir/ganeti,andir/ganeti,onponomarev/ganeti,leshchevds/ganeti,mbakke/ganeti,leshchevds/ganeti,ganeti/ganeti,andir/ganeti,ganeti/ganeti,onponomarev/ganeti,leshchevds/ganeti,mbakke/ganeti