libext2fs: find inode goal when allocating blocks

libext2fs: find inode goal when allocating blocks

Try to be a little smarter about where we go to allocate blocks for a
inode.  For a given inode and logical offset, set the goal as if the
file were physically continuous.  If it's bmapped, just start looking
at wherever lblk 0 is.  If that's not possible (the file has no
lblk>pblk mappings, inline data, etc.) then start looking in the
inode's block group.

[ Fixed memory leak --tytso ]

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>