LU-7131 utils: add "--erase-param" option to tunefs.lustre

LU-7131 utils: add "--erase-param" option to tunefs.lustre

This patch is to fix the following issues:

- A new option "--erase-param" is added to tunefs.lustre, which allows
to remove all instances of a specific parameter.

- The behavior of option "--param" is improved a little. It will erase
all previously stored instances of the parameter, and then store all
new values specified in the command line.

- For zfs only, the patch introduces a "null value" rule in the form
of "<key>=" to mark a property to be removed from dataset by
zfs_write_ldd() finally.

- To keep the right semantics, if "--erase-params" is specified, all
old parameters should be erased before any new changes are done.

- test_89 conf-sanity.sh is added to verify these new features.

Seagate-bug-id: MRP-153
Signed-off-by: Nikitas Angelinas <nikitas.angelinas@seagate.com>
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: Ibc8d81227045471b8e5c56c7faf1275ad8bbbf86
Tested-by: Elena Gryaznova <elena.gryaznova@seagate.com>
Reviewed-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Reviewed-by: Vitaly Fertman <vitaly.fertman@seagate.com>
Reviewed-on: https://review.whamcloud.com/16359
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Tested-by: Jenkins
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>