Ensure config files are not overwritten in RPM upgrade

In order to ensure that configuration files do not get overwritten when
upgrading an RPM, it is not sufficient to mark them as configuration. You
have to use the 'noreplace' parameter to make sure, they are never
overwritten. Added this parameter for the /etc/elasticsearch directory
as well as the /etc/sysconfig/elasticsearch file.

In addition, the post remove script now only deletes the user in case of
a package removal (and does nothing on package upgrade).

Closes #3123