staging: lustre: lnet: fix build warning in module.c

staging: lustre: lnet: fix build warning in module.c

With the latest patches from Neil, we are now getting a build warning:

drivers/staging/lustre/lnet/selftest/module.c: In function ‘lnet_selftest_init’:
drivers/staging/lustre/lnet/selftest/module.c:98:10: warning: ‘rc’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   return rc;
          ^~

So fix this up by giving a default error value to rc.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>