ocfs2: set i_mode on disk during acl operations

ocfs2_set_acl() and ocfs2_init_acl() were setting i_mode on the in-memory
inode, but never setting it on the disk copy. Thus, acls were some times not
getting propagated between nodes. This patch fixes the issue by adding a
helper function ocfs2_acl_set_mode() which does this the right way.
ocfs2_set_acl() and ocfs2_init_acl() are then updated to call
ocfs2_acl_set_mode().

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>