Conntrack headers fails to parse.

Conntrack headers fails to parse.

The extra headers added to the packet when it return from ovs after a
conntrack operation causes deserialization error when the packet is
punted to the controller.

Added ct_clear action once the packet is returned from conntrack in
table=47

table=47, n_packets=50, n_bytes=4887,
priority=6,ct_state=+snat,ip,metadata=0x30d40/0xfffffe
actions=load:0x30d48->OXM_OF_METADATA[0..23],
load:0->NXM_OF_IN_PORT[],ct_clear,resubmit(,21)

NETVIRT-1383 Traffic to the PNF from a VM without FIP fails(SNAT
conntrack)

Change-Id: Ib34109b7fe3c7aa1df105c8504394291031e68d6
Signed-off-by: Aswin Suryanarayanan <asuryana@redhat.com>