RFR(S): 8191863: [s390] Fix CDS: some bytecode rewriting doesn't depend on RewriteControl

Hi, can I please have a review for the following small, s390-only change which fixes CDS on s390: http://cr.openjdk.java.net/~simonis/webrevs/2017/8191863/ https://bugs.openjdk.java.net/browse/JDK-8191863 The problem was that mistakenly rewrote zputfield into fast_zputfield although the active RewriteControl instance indicated that we shouldn't rewrite bytecodes. With this change, all the CDS and upcoming AppCDS jtreg pass on Linux/s390. Thank you and best regards, Volker