Tiny  improvement in paths

This patch allows to run devstack-vm-gate-wrap.sh outside
$WORKSPACE directory. Without this patch script fails with
error that logs/* paths are not found.

Change-Id: Ia6d0723fd8dc5dde60fba76783678053069a0a86
Pretty up the post-run df call

Just easier to read.

Change-Id: Ib0dd8a92ef2b7143cfbe4aef50823f2254c77cff
Merge "Tiny  improvement in paths"
Merge "Pretty up the post-run df call"