CLOUDSTACK-7855: NIC3 should set MTU and not NIC1 for storage network nic

The fix also persists the configuration in /etc/network/interfaces

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
CVE­2014­3566: Avoid using SSLv3 on apache2 that runs on SSVM

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>