staging/lustre/obdclass: fix false used uninitialized warning

Got below warning when building lustre with 4.7.3.
drivers/staging/lustre/lustre/obdclass/llog_test.c: In function ‘
llog_test_init’:
drivers/staging/lustre/lustre/obdclass/llog_test.c:1058:28: warning: ‘
lvars.module_vars’ is used uninitialized in this function
[-Wuninitialized]

Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>