ocfs2: move dquot_initialize() in ocfs2_delete_inode() somewhat later

Move dquot_initalize() call in ocfs2_delete_inode() after the moment we
verify inode is actually a sane one to delete.  We certainly don't want
to initialize quota for system inodes etc.  This also avoids calling
into quota code from downconvert thread.

Add more details into the comment why bailing out from
ocfs2_delete_inode() when we are in downconvert thread is OK.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>