ovs-vswitchd.at: Add test for switch over to another ovs-vswitchd.

Test the switch over to inactive ovs-vswitchd process when user
kill the currently active ovs-vswitchd.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>
datapath: Add support for RHEL-7 / CentOS-7 kernel.

This patch mostly is related to tunnel API where RHEL 7
kernel API are not in-sync with newer linux kernel API. So
extra checks are required to check for parameters of API.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jiri Benc <jbenc@redhat.com>