LU-8361 lfsck: detect Lustre device automatically

LU-8361 lfsck: detect Lustre device automatically

Originally, when start/stop/query LFSCK, the user needs to
specify the Lustre device via "-M" option explicitly. Even
if there is only single Lustre device on current server or
the user wants to start the LFSCK on all devices with the
"-A" option specified, the "-M" option is still required.
Such requirement is inconvenient. This patch enhances the
LFSCK user interfaces to allow the user to run the LFSCK
commands without "-M" specified. Instead, it will select
the available Lustre device on current server automatically.
But under the following cases the "-M" option is still
required: if there are multiple devices on current server
those belong to different Lustre filesystems, or if "-A"
option is not specified and there are multiple devices on
current server.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I291b958440b2409c93cdc8ef3a5e3fbe14885141
Reviewed-on: http://review.whamcloud.com/21596
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>