debian: Skip systemctl redirect.

debian: Skip systemctl redirect.

After some experimentation on Ubuntu15.04, I see the
following behavior.

1. If you install openvswitch-switch with 'apt-get install',
then you automatically get a upstart and systemd config files
for openvswitch. The integration with 'interfaces' fails
because both the upstart and systemd jobs do not have logic
to handle it.

The above behavior will likely get fixed soon in upstream
Ubuntu.

2. If you install openvswitch-switch via the packages
created from the openvswitch repo, there is no systemd or
upstart conf files installed. But systemd notices this
and creates a runtime openvswitch conf file which does
nothing but call back the sysv startup script.

In the above case when you call
"/etc/init.d/openvswitch-switch start", it inturn calls
"/bin/systemctl start openvswitch-switch.service" and
that inturn again calls "/etc/init.d/openvswitch-switch start".
But the above for some reason simply hangs. It looks like a call
to ifup when invoked in this manner does not return.
I am not sure why this is happening.

We can avoid the above behavior completely by skipping the
systemctl redirect as done in this commit. This should fix
both 1. and 2. above.

Signed-off-by: Gurucharan Shetty <guru@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>