target: Don't return success from module_init() if setup fails

commit 0d0f9dfb31e0a6c92063e235417b42df185b3275 upstream.

If the call to core_dev_release_virtual_lun0() fails, then nothing
sets ret to anything other than 0, so even though everything is
torn down and freed, target_core_init_configfs() will seem to succeed
and the module will be loaded.  Fix this by passing the return value
on up the chain.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>