Remove unnecessary openvswitch-datapath-dkms package

Kernel openvswitch module is included in Ubuntu Trusty 14.04

# modinfo openvswitch
filename:       /lib/modules/3.13.0-32-generic/kernel/net/openvswitch/openvswitch.ko
license:        GPL
description:    Open vSwitch switching datapath
srcversion:     47D3079FB6731A4B46CED6E
depends:        libcrc32c,vxlan,gre
intree:         Y
vermagic:       3.13.0-32-generic SMP mod_unload modversions 
signer:         Magrathea: Glacier signing key
sig_key:        5E:3C:0F:9C:A6:E3:65:43:53:5F:A2:BB:5B:70:9E:84:F1:6D:A7:C7
sig_hashalgo:   sha512