jdeps generates illegal dot file containing ranksep=0,600000

jdeps should format double with no localization.

$ hg diff src/jdk.jdeps/share/classes/com/sun/tools/jdeps/ModuleDotGraph.java
diff --git a/src/jdk.jdeps/share/classes/com/sun/tools/jdeps/ModuleDotGraph.java b/src/jdk.jdeps/share/classes/com/sun/tools/jdeps/ModuleDotGraph.java
--- a/src/jdk.jdeps/share/classes/com/sun/tools/jdeps/ModuleDotGraph.java
+++ b/src/jdk.jdeps/share/classes/com/sun/tools/jdeps/ModuleDotGraph.java
@@ -44,6 +44,7 @@
 import java.util.Deque;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -329,7 +330,7 @@
 
                 out.format("digraph \"%s\" {%n", name);
                 out.format(" nodesep=.5;%n");
- out.format(" ranksep=%f;%n", attributes.rankSep());
+ out.format((Locale)null, " ranksep=%f;%n", attributes.rankSep());
                 out.format(" pencolor=transparent;%n");
                 out.format(" node [shape=plaintext, fontcolor=\"%s\", fontname=\"%s\","
                                 + " fontsize=%d, margin=\".2,.2\"];%n",