GFS2: O_TRUNC not working on stuffed files across cluster

This patch replaces a statement that got dropped out by accident.
Without the patch, truncates on stuffed (very small) files cause
those files to have an unpredictable size.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>