GFS2: make sure S_NOSEC flag isn't overwritten

At the end of gfs2_set_inode_flags inode->i_flags is set to flags, so
we should be modifying flags instead of inode->i_flags, so it isn't
overwritten.

Signed-off-by: Benjamin Marzinski <bmarzins redhat com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>