consumer: fix tcmulib_initialize check
consumer: fix tcmulib_initialize check

It's a pointer so check for NULL like normal people.

Signed-off-by: Mike Christie <39daeb1549a929782e38aa87c4e3da7f3844b09a@redhat.com>

agrover/tcmu-runner,open-iscsi/tcmu-runner,open-iscsi/tcmu-runner