LU-1526 tests: Adapt oos to the new grant and osd-zfs behavior

LU-1526 tests: Adapt oos to the new grant and osd-zfs behavior

This patch is backported from commit 938947f of LU-1415 to
support oos interoperating testing with 2.4 server.

The patch moves the oos checking codes from oos.sh and
oos2.sh into common function oos_full() in test-framework.sh.

The oos_full() allows 1% of total space in bavail because of
delayed allocation with ZFS which might release some free space
after txg commit.

Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I8933a6c8614a96d7bab5689c9d3e3a1f59bbc133
Reviewed-on: http://review.whamcloud.com/4986
Tested-by: Hudson
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>