LU-10482 flr: enhance "lfs find" to add mirror options

LU-10482 flr: enhance "lfs find" to add mirror options

This patch adds the following mirror related search
options to "lfs find" command:

[[!] --mirror-count|-N [+-]n]
[[!] --mirror-state <[^]state>]

--mirror-count|-N indicates mirror count.
--mirror-state indicates mirrored file state.

A mirrored file can be one of the following states:
ro indicates the mirrored file is in read-only state.
   All of the mirrors contain the up-to-date data.
wp indicates the mirrored file is being written.
sp indicates the mirrored file is being resynchronized.

Change-Id: I3c8f5c8bb6518ba4bd73fc2f164dd52afdfac211
Signed-off-by: Jian Yu <jian.yu@intel.com>
Reviewed-on: https://review.whamcloud.com/31069
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>