LU-3264 tests: support failover testing with ZFS

LU-3264 tests: support failover testing with ZFS

This patch improves test-framework.sh to support failover testing with
ZFS under shared storage configuration.

After formatting a ZFS target, "cachefile=none" property will be set
on the ZFS storage pool so that the pool is not automatically imported
on system startup. And then the pool will be exported so as to leave
the import and export operations handled by mount_facet() and stop().

For SOFT failure mode (unmount and mount), "zpool export …" will be
run on the active server node to export the ZFS storage pool, and
"zpool import -f …" will be run on the failover partner node to import
the pool.

For HARD failure mode (power off and on), since the "cachefile=none"
property has been set on the ZFS storage pool on the active server
node, after the node is power-cycled, the pool will not be imported.
Then on the failover partner node, "zpool import -f …" can be run to
import the pool.

This is a reworked patch with fixes merged in.

Formerly Change-Id: I6b9646cb36f7fa4924af03a055ccb137187843a5
Formerly Reviewed-on: http://review.whamcloud.com/6258
Formerly Change-Id: I63ac141fdefcace99a1cf7c366e15f0067fa2a56
Formerly Reviewed-on: http://review.whamcloud.com/6358
Formerly Change-Id: I83678fd8b67de87f5174017634f108e6ae5b30e0
Formerly Reviewed-on: http://review.whamcloud.com/6408

Test-Parameters: envdefinitions=PTLDEBUG=-1,DEBUG_SIZE=128 mdtfilesystemtype=zfs mdsfilesystemtype=zfs ostfilesystemtype=zfs clientdistro=el6 serverdistro=el6 clientarch=x86_64 serverarch=x86_64 clientcount=4 osscount=2 mdscount=2 austeroptions=-R failover=true useiscsi=true testlist=recovery-double-scale
Signed-off-by: Jian Yu <jian.yu@intel.com>
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: I6d2fffede5de7a7d4a6bde3d62dd7c6cb60f63fa
Reviewed-on: http://review.whamcloud.com/6429
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>