Revert "Prevent running pg_basebackup as root"
This reverts commit
7bae0ad, as this is not ideal with the tar format,
and we may want to explore more options like what is done by tar with
some equivalents of --owner and --group, but for pg_basebackup.
Per complaints from Magnus Hagander and Stephen Frost.
Discussion: https://postgr.es/m/
20200205172259.GW3195@tamriel.snowman.net