libext2fs: don't update the summary counts when doing implied cluster allocation

libext2fs: don't update the summary counts when doing implied cluster allocation

When we're appending a block to a directory file or the journal file,
and the new block is part of a cluster that has already been allocated
to the file (implied cluster allocation), don't update the bitmap or
the summary counts because that was performed when the cluster was
allocated.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>