staging: lustre: osc: tidy up osc_init()

A module_init() function that registers the services
of the module should do that last, after all other
initialization has succeeded.
This patch moves the class_register_type() call to the
end and ensures everything else that might have been
set up, is cleaned up on error.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>