idmap: always seteuid to the owner of the namespace

idmap: always seteuid to the owner of the namespace

simplify the condition for setting the euid of the process.  Now it is
always set when we are running as root, the issue was introduced with
the commit 52c081b02c4ca4432330ee336a60f6f803431e63

Changelog: 2018-11-24 - seh - enforce that euid only gets set to ruid if
   it currently == 0 (i.e. really was setuid-*root*).

Closes: https://github.com/genuinetools/img/issues/191
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Serge Hallyn <shallyn@cisco.com>