LU-17486 ldiskfs: fix race in ext4_destroy_inode

LU-17486 ldiskfs: fix race in ext4_destroy_inode

ext4_i_callback() can race with the access to i_reserved_data_blocks
in ext4_destroy_inode() when used with preemption-enabled kernel.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I69c6bcfbb24e6c07d28ebcd2bdd9d9e6f06ec8d1
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53868
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>