Remove OVS installation in DF unstack
Remove OVS installation in DF unstack

We currently install OVS from source on stack,
This removes the installation correctly on unstack

Change-Id: I47caf83ce67b5ea6054429791b5d342146e229c0

FrankDuan/df_code,neoareslinux/dragonflow,openstack/dragonflow,neoareslinux/dragonflow,openstack/dragonflow,openstack/dragonflow,FrankDuan/df_code,FrankDuan/df_code