LU-10901 build: Update ZFS/SPL to 0.7.8

LU-10901 build: Update ZFS/SPL to 0.7.8

This skips 0.7.7 due to regression fixed in 0.7.8

https://github.com/zfsonlinux/zfs/releases/tag/zfs-0.7.8
https://github.com/zfsonlinux/zfs/releases/tag/zfs-0.7.7

Lustre-change: https://review.whamcloud.com/31949
Lustre-commit: 33fa3ca05b5bb6abbcef01444c3f383d876ecba9

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Icd6a21793a5f7502c88121def8d86d9aa48c6ae8
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-on: https://review.whamcloud.com/32070
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>