Long story short, some kernels before 3.15 had an issue with using su
in a container when the network namespace was --net=host. The gate
has a 3.10 and a 3.13 kernel and has a problem with this. This changes
everything to use sudo

backport: liberty
Partially-Implements: blueprint functional-testing-gate
Change-Id: I4d79ccaa1cddffcc8393f64e7e1be2538efe33e5