Remove ZFS pool entry for ysul from pillar

Summary:
On ysul, ZFS is not installed, the system uses UFS. To avoid errors when running
salt 'ysul' state.apply roles/core, the ZFS pool configuration must be removed
from the pillar nodes.sls.

Ref T2315

Reviewers: dereckson, Duranzed

Reviewed By: dereckson

Subscribers: Duranzed, dereckson

Maniphest Tasks: T2315

Differential Revision: https://devcentral.nasqueron.org/D4088