Backporting -md5skip command line option from h2o-dev

Author: mmalohlava

src/main/java/water/H2O.java

@@ -418,10 +418,10 @@ private static InetAddress guessInetAddress(List<InetAddress> ips) {
       // using google's DNS server as an external IP to find
       // Add a timeout to the touch of google.
       // https://0xdata.atlassian.net/browse/HEX-743
-      s = new Socket(); 
+      s = new Socket();
       // only 3000 milliseconds before giving up
       // Exceptions: IOException, SocketTimeoutException, plus two Illegal* exceptions
-      s.connect(new InetSocketAddress("8.8.8.8", 53), 3000); 
+      s.connect(new InetSocketAddress("8.8.8.8", 53), 3000);
       m+="Using " + s.getLocalAddress() + "\n";
       return s.getLocalAddress();
     } catch( java.net.SocketException se ) {
@@ -708,6 +708,7 @@ public static class OptArgs extends Arguments.Opt {
     public String single_precision = null;
     public String beta = null;
     public String mem_watchdog = null; // For developer debugging
+    public boolean md5skip = false;
   }
 
   public static void printHelp() {

src/main/java/water/Paxos.java

@@ -39,7 +39,7 @@ public abstract class Paxos {
   static synchronized int doHeartbeat( H2ONode h2o ) {
     // Kill somebody if the jar files mismatch.  Do not attempt to deal with
     // mismatched jars.
-    if( !h2o._heartbeat.check_jar_md5() ) {
+    if( !H2O.OPT_ARGS.md5skip && !h2o._heartbeat.check_jar_md5() ) {
       if( H2O.CLOUD.size() > 1 ) {
         Log.warn("Killing "+h2o+" because of H2O version mismatch (md5 differs).");
         UDPRebooted.T.mismatch.send(h2o);