ofproto: Send only one OFPT_FLOW_REMOVED message when a flow expires.

Commit 15aaf59932a3 (ofproto: Add global locking around flow table
changes.) introduced doubled messages for expirations.

Reported-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>
ofp-actions: Distinguish OF1.1/1.2 push_mpls from OF1.3+.

In OpenFlow 1.1 and 1.2, the push_mpls action pushes the MPLS label after
any existing VLAN tag.  In OpenFlow 1.3, it pushes the label before any
existing VLAN tag.  Until now, the action parser didn't distinguish these
cases.  This commit adds support.  Nothing yet actually changes the
behavior of push_mpls.

enum ofpact_mpls_position contributed by Ben Pfaff.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>
odp-execute: Fix possible segfault.

In current code, the odp_execute_actions() function does not check
the value of "userspace" function pointer before invoking it.  This
patch adds a check for it.

Signed-off-by: Alex Wang <alexw@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>