datapath: Handle NF_REPEAT in conntrack action.

datapath: Handle NF_REPEAT in conntrack action.

Upstream commit:
    commit 5b6b929376a621e2bd3367f5de563d7123506597
    Author: Jarno Rajahalme <jarno@ovn.org>
    Date:   Thu Mar 10 10:54:21 2016 -0800

    openvswitch: Handle NF_REPEAT in conntrack action.

    Repeat the nf_conntrack_in() call when it returns NF_REPEAT.  This
    avoids dropping a SYN packet re-opening an existing TCP connection.

    Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
    Acked-by: Joe Stringer <joe@ovn.org>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>