LU-1664 build: Feed spl/zfs Module.symvers to osd-zfs

This hunk, from Orion, should also be included to make sure that osd-zfs
can access spl/zfs's Module.symvars files.

Change-Id: Ic4e514c1f1f8f026353c4a8c686c0e4c389663a1
Signed-off-by: Li Wei <liwei@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/3454
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>