staging: lustre: lnet: fix improper return value

At the end of function lstcon_group_info(), "return 0" seems improper.
It may be better to return the value of rc.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=188811



Signed-off-by: Pan Bian <bianpan2016@163.com>
Acked-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>