Restore thread interrupt after SyncFailsafe sleep is interrupted. Addresses failsafe-lib#63.

Author: jhalterman

src/main/java/net/jodah/failsafe/SyncFailsafe.java

@@ -143,6 +143,7 @@ private <T> T call(Callable<T> callable) {
         try {
           Thread.sleep(execution.getWaitTime().toMillis());
         } catch (InterruptedException e) {
+          Thread.currentThread().interrupt();
           throw new FailsafeException(e);
         }