We've applied a workaround since 1.0.0 to allow building Tez as root(
BIGTOP-1815). By that time there's no user namespace in docker yet. But now the feature is available, hence we should drop the workaround.
We encountered the same issue when building Zeppelin 0.7(
BIGTOP-2689), which has been addressed by specifying --user jenkins when starting docker containers. Therefore the fix should be simply remove the allow-root configuration.