ext4: add checksum calculation when clearing UNINIT flag in ext4_new_inode

ext4: add checksum calculation when clearing UNINIT flag in ext4_new_inode

(cherry picked from commit 23712a9c28b9f80a8cf70c8490358d5f562d2465)

When initializing an uninitialized block group in ext4_new_inode(),
its block group checksum must be re-calculated.  This fixes a race
when several threads try to allocate a new inode in an UNINIT'd group.

There is some question whether we need to be initializing the block
bitmap in ext4_new_inode() at all, but for now, if we are going to
init the block group, let's eliminate the race.

Signed-off-by: Frederic Bohe <frederic.bohe@bull.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>