rhel: make openvswitch service start return when ready

In OVS 2.6 openvswitch systemd service was changed to use BindsTo
instead of Requires for sub-services but also removed them from After

This made main openvswitch service return before sub-services were ready
breaking scripts which assumed everything is ready after systemctl start
e.g. in OpenStack CI infra [1] is calling ovs-vsctl immediately after
service start exposing a race in virtualized CI environment:
2017-02-09T23:11:12.498Z|00007|bridge|INFO|ovs-vswitchd (Open vSwitch) 2.6.1
but ovs-ctl tried to access it few msec too early:
2017-02-09 23:11:12.352493 | ovs-vsctl: unix:/var/run/openvswitch/db.sock: database connection failed (No such file or directory)

Solution is to add ordering dependencies, BindsTo/Requires do not ensure it [2]

[1] https://github.com/openstack-infra/devstack-gate/blob/c435a724bd257b22a2e39e8e9125c11302a8c81d/functions.sh#L1057-L1078

[2] https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Requires=

Fixes: 84ad120 ("rhel: Improved Systemd Integration")
Signed-off-by: Alan Pevec <alan.pevec@redhat.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Russell Bryant <russell@ovn.org>

AUTHORS.rst

@@ -33,6 +33,7 @@ Name                            Email
 =============================== ===============================================
 Aaron Conole                    aconole@redhat.com
 Aaron Rosen                     arosen@clemson.edu
+Alan Pevec                      alan.pevec@redhat.com
 Alexander Duyck                 alexander.h.duyck@redhat.com
 Alexandru Copot                 alex.mihai.c@gmail.com
 Alexei Starovoitov              ast@plumgrid.com

rhel/usr_lib_systemd_system_openvswitch.service

@@ -1,7 +1,7 @@
 [Unit]
 Description=Open vSwitch
 Before=network.target network.service
-After=network-pre.target
+After=network-pre.target ovsdb-server.service ovs-vswitchd.service
 PartOf=network.target
 BindsTo=ovsdb-server.service
 BindsTo=ovs-vswitchd.service