Remove extremely ugly way of copying a Configuration object
that used a String representation that got immediately parsed again
with a custom parser.
This would break if anything of the output format would have changed,
and is completely unnecessary because there exists already a single
method that does exactly what is needed here.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14617 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c