Check the return value from DropRoot() Unlike the other brillo::Minijail methods, this one can fail if the username lookup does not succeed. BUG=chromium:670985 TEST=buildbots Change-Id: Id1d5059fb155c1a227033af0eba837ab37e96fe9 Reviewed-on: https://chromium-review.googlesource.com/416302 Commit-Ready: Kevin Cernekee <[email protected]> Tested-by: Kevin Cernekee <[email protected]> Reviewed-by: Mattias Nissler <[email protected]> Reviewed-by: Jorge Lucangeli Obes <[email protected]>