[ZFSOnLinux] Allow devstack bootstrap in Ubuntu > 16.04
[ZFSOnLinux] Allow devstack bootstrap in Ubuntu > 16.04

The package seems to be present and maintained
in the ubuntu repositories for all releases
following Xenial Xerus.

[1] https://packages.ubuntu.com/search?keywords=zfsutils-linux

Change-Id: If212e0482b360f3c3888918242dba6a710ab2818
Needed-By: https://review.openstack.org/#/c/604929/

openstack/manila,openstack/manila