ext4: mark inode dirty after initializing the extent tree

We should mark the inode dirty only after initializing the extent
tree.  Also if we fail during extent initialization we need
to call DQUOT_FREE_INODE.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>