LU-6020 kerberos: proper sg list initialization

LU-6020 kerberos: proper sg list initialization

This patch adds sg_init_table() calls in order
to have proper sg list initialization including
magics, tables sizes, etc.

Without it, when using kernels with CONFIG_DEBUG_SG
option, the following crash can happen:

kernel BUG at include/linux/scatterlist.h:65!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
last sysfs file: /sys/devices/system/cpu/online
CPU 0

Pid: 4911, comm: ptlrpcd_3 Not tainted 2.6.32-431 #7                  /D525MWV
RIP: 0010:[<ffffffffa0b60170>]  [<ffffffffa0b60170>] krb5_make_checksum+0x750/0x770 [ptlrpc_gss]

Change-Id: Ic6c52c8b15393d8d7f67f4bf675c1f57cf27004a
Signed-off-by: Andrew Perepechko <andrew.perepechko@seagate.com>
Reviewed-on: http://review.whamcloud.com/13631
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>