Move PATH set earlier

Checking the logs for a f20 run you'll see

---
 + ./safe-devstack-vm-gate-wrap.sh
 sudo: service: command not found
 22 Jul 21:24:41 ntpdate[1551]: adjust time ...
 sudo: service: command not found
---

We already went through this path issue with [1] so just move it
earlier before anything runs

[1] https://review.openstack.org/#/c/91655/

Change-Id: Ie6bd27342b0ba0f0fba0a1d3695f108128d4366e
Merge "Move PATH set earlier"