LU-2571 lfsck: run lfsck on server node

LU-2571 lfsck: run lfsck on server node

Usually we run e2fsck on OST and MDS nodes, and run lfsck on clients,
but it's not necessary to install e2fsprogs rpm on clients.
So, if lfsck is not found on client, we will try server node instead.

Test-Parameters: testlist=lfsck
Signed-off-by: Liu Ying <emoly.liu@intel.com>
Change-Id: I3979dc0236e81163f3283eac3148c36c8ddccf63
Reviewed-on: http://review.whamcloud.com/5139
Tested-by: Hudson
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>