debian: Change openvswitch restart logic for kernel package.

debian: Change openvswitch restart logic for kernel package.

Currently, every time we install the non-dkms openvswitch kernel package,
we restart openvswitch. This has no useful effect when an Open vSwitch kernel
module is already loaded, because "/etc/init.d/openvswitch restart" does not
load the new version of the kernel module.

With this patch, we start openvswitch if there is no kernel module
currently loaded (which is a case for a fresh install of openvswitch). This
will load the kernel module.

If someone wants to use the latest kernel module after an upgrade, they need
to run "/etc/init.d/openvswitch-switch force-reload-kmod" manually.

Issue #13556
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>