infra/image: Make fixnet and fixipaip services active by default

The services are now active by default and do not need to be activated
after IPA has been deployed.

The fixnet service is always activated and removes all lines containing
the hostname from /etc/hosts and adds a new line with the IP and the
hostname with and without domain. If IPA is deployed with DNS (the
config file /etc/named.conf exists and there is a '^dyndb "ipa"' line
in /etc/named.conf) then /etc/resolv.conf is also changed to use the
local DNS server.

The fixipaip service is now also always activated, but only started IF
IPA has been deployed and the ipa service was started before.

infra/image/build.sh is not actvating the services anymore, the services
are now actiavted in alll dockerfiles.