Replace a usage of the deprecated root_helper option
Replace a usage of the deprecated root_helper option

This change replaces a usage of the deprecated root_helper option
by the usage of get_root_helper result.

Change-Id: Icfc698243784557cbf987a817c13d0b80969e5d3
Closes-Bug: #1297145

gkotton/vmware-nsx,gkotton/vmware-nsx