ovs-sandbox: Initialize database before starting ovs-vswitchd.

ovs-sandbox: Initialize database before starting ovs-vswitchd.

Otherwise ovs-vswitchd can't immediately start working (until some other
call to ovs-vsctl initializes the database).  This is most obvious if one
runs "ovs-vsctl list Open_vSwitch ." as the first command, because the
output will not show the changes that ovs-vswitchd will make to the
database at startup (in particular initializing datapath_types and
iface_types), which is confusing.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Russell Bryant <rbryant@redhat.com>