LU-5091 build: Support alternate locations of libzfs.so

Due to the change for with-zfs-devel (LU-3497), also add support to
search for libzfs.so along with the alternate locations supplied with
the header files.
Also need to unpack zfs{,-devel}.  The zfs RPM is needed because it
has the actual libraries in it and the zfs-devel RPM only has un-
versioned symlinks to the libraries in the zfs RPM.
This will all change one day when we have a libzfs RPM per
https://github.com/zfsonlinux/zfs/issues/2329 and it looks like it
could be one day soon: https://github.com/zfsonlinux/zfs/pull/2341.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Signed-off-by: Brian J. Murrell <brian.murrell@intel.com>
Change-Id: Ic78bd0eb88d8ab0f2456b8cf684bb8b9c0c0833a
Reviewed-on: http://review.whamcloud.com/10401
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>