LU-6105 build: Update SPL/ZFS version to 0.6.3-1.2

Update to latest release of ZFS & SPL:
Includes fixes compatibility with kernels up through 3.17 and fixes
SPL mutex_exit races.

Also address redefinition of SHRINK_STOP between SPL and Lustre.  Both
use the same numeric value -1 but in ways that cause gcc to complain.

Test-Parameters: mdtfilesystemtype=zfs mdsfilesystemtype=zfs ostfilesystemtype=zfs testlist=sanity,sanity,sanity,sanity,sanity,sanity,sanity
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: I2ba0119d3535beb3bae1b47021c5a167ce25e129
Reviewed-on: http://review.whamcloud.com/13322
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Tested-by: Jenkins
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>