reiserfs: Relax reiserfs_xattr_set_handle() while acquiring xattr locks

Fix remaining xattr locks acquired in reiserfs_xattr_set_handle()
while we are holding the reiserfs lock to avoid lock inversions.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>