Prevent duplicates in /etc/resolv.conf

Updated the function setupDNS to check for already existing identical
entries to prevent creating duplicates in /etc/resolv.conf.
Allow preconfiguring of s390 network cards

The default configuration DASD 191 is checked for a parm file with the
name <LINUX_USER_ID>.PARM-S11.
If it is found the parameters are exported and used to set up the
network with setupNetworkInterfaceS390.