Update NEWS file for 2.16.0 beta2
Update NEWS file for 2.16.0 beta2

Update both major and minor changes since beta 1 including changes
inherited from older branches.

Signed-off-by: Viktor Bachraty <a13ea37fcfcda126dc54f94389ded93f402eee93@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

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