Set locales to avoid downstream problems

base/centos7-bundle:2021.03.01

 FROM docker.km3net.de/base/centos:7
  MAINTAINER Tamas Gal <tgal@km3net.de>
 
+ ENV LANG en_US.UTF-8  
+ ENV LANGUAGE en_US:en  
+ ENV LC_ALL en_US.UTF-8   
+
  RUN yum install -y centos-release-scl epel-release
  RUN yum install -y man sed cygpath grep test csh tar vim lftp zsh \
                     bzip2-devel gzip libproxy libgpg-error openssh-server \