[PATCH] travis: switch to using root user

[Stephen Finucane]

On Wed, 2017-09-06 at 02:13 +1000, Daniel Axtens wrote:
> When I pushed the last change, I noticed that Travis was beginning
> to fail due to db permission errors. This is a trivial fixup.
> 
> Signed-off-by: Daniel Axtens <dja at axtens.net>

Reviewed-by: Stephen Finucane <stephen at that.guru>

Probably worth backporting too. If we don't have Travis enabled on that branch
we probably should fix that.