add missing interrupt restore on InterruptedException

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@769409 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/lucene/store/Lock.java

@@ -93,6 +93,7 @@ public abstract class Lock {
       } catch (InterruptedException e) {
         // In 3.0 we will change this to throw
         // InterruptedException instead
+        Thread.currentThread().interrupt();
         throw new IOException(e.toString());
       }
       locked = obtain();