LU-8999 quota: fix issue of multiple call of seq start

LU-8999 quota: fix issue of multiple call of seq start

Multiple call of lprocfs_quota_seq_start could change the block
orders in the lower level of the quota tree, which will cause
quota entries to be skipped.

This patch also fix a problem in walk_tree_dqentry, which some
entries could be skipped for the "index" can be added even if
a valid quota entry has been found.

Lustre-commit: 07fdba2244e748e1721232abc52617209a544b87
Lustre-change: http://review.whamcloud.com/31721

Change-Id: I21f31647ebc15d34dc2021a2d8c5ad40fe128535
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: https://review.whamcloud.com/32567
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>