Add fix for earlier jdks which used InitialHeap instead of MinHeap

Author: mark-vieira

distribution/tools/launchers/src/main/java/org/elasticsearch/tools/launchers/JvmOption.java

@@ -73,6 +73,11 @@ public static boolean isMinHeapSpecified(final Map<String, JvmOption> finalJvmOp
         return minHeapSize != null && minHeapSize.isCommandLineOrigin();
     }
 
+    public static boolean isInitialHeapSpecified(final Map<String, JvmOption> finalJvmOptions) {
+        JvmOption initialHeapSize = finalJvmOptions.get("InitialHeapSize");
+        return initialHeapSize != null && initialHeapSize.isCommandLineOrigin();
+    }
+
     public static long extractMaxDirectMemorySize(final Map<String, JvmOption> finalJvmOptions) {
         return Long.parseLong(finalJvmOptions.get("MaxDirectMemorySize").getMandatoryValue());
     }

distribution/tools/launchers/src/main/java/org/elasticsearch/tools/launchers/MachineDependentHeap.java

@@ -37,6 +37,9 @@
 
 import static java.lang.Math.max;
 import static java.lang.Math.min;
+import static org.elasticsearch.tools.launchers.JvmOption.isInitialHeapSpecified;
+import static org.elasticsearch.tools.launchers.JvmOption.isMaxHeapSpecified;
+import static org.elasticsearch.tools.launchers.JvmOption.isMinHeapSpecified;
 
 /**
  * Determines optimal default heap settings based on available system memory and assigned node roles.
@@ -66,7 +69,7 @@ public MachineDependentHeap(SystemMemoryInfo systemMemoryInfo) {
     public List<String> determineHeapSettings(Path configDir, List<String> userDefinedJvmOptions) throws IOException, InterruptedException {
         // TODO: this could be more efficient, to only parse final options once
         final Map<String, JvmOption> finalJvmOptions = JvmOption.findFinalOptions(userDefinedJvmOptions);
-        if (JvmOption.isMaxHeapSpecified(finalJvmOptions) || JvmOption.isMinHeapSpecified(finalJvmOptions)) {
+        if (isMaxHeapSpecified(finalJvmOptions) || isMinHeapSpecified(finalJvmOptions) || isInitialHeapSpecified(finalJvmOptions)) {
             // User has explicitly set memory settings so we use those
             return Collections.emptyList();
         }