java: make runSync interrupt the context on which it waits

Interrupting a thread which is blocked waiting for an isolate to
complete which was started via runSync() should interrupt the isolate.
The waiter should return only after isolate terminated.

I think this is what users would expect to happen when interrupting a
foreground process.

java/runjava/src/main/java/io/osv/Context.java

@@ -48,4 +48,8 @@ public final class Context {
     public LogManagerWrapper getLogManagerWrapper() {
         return logManagerWrapper.get();
     }
+
+    public void interrupt() {
+        mainThread.interrupt();
+    }
 }

java/runjava/src/main/java/io/osv/ContextIsolator.java

@@ -87,8 +87,17 @@ public class ContextIsolator {
 
     public void runSync(String[] args) throws Throwable {
         Context context = run(args);
-        if (context != null) {
-            context.join();
+        if (context == null) {
+            return;
+        }
+
+        while (true) {
+            try {
+                context.join();
+                return;
+            } catch (InterruptedException e) {
+                context.interrupt();
+            }
         }
     }