[JVM] Reset eof to false after seeking

Fixes tests in S16-io/eof.t (rakudo/rakudo#1322).

After a call to seek the state of eof might very well have changed. Better
reset it to false so that it is properly checked the next time eof is tested.

src/vm/jvm/runtime/org/perl6/nqp/io/FileHandle.java

@@ -92,6 +92,8 @@ public void seek(ThreadContext tc, long offset, long whence) {
         }
         /* Reset readBuffer since content is out of sync after fc.position. */
         readBuffer = null;
+        /* Reset eof since it might have changed; needs to be checked anew. */
+        eof = false;
     }
 
     public long tell(ThreadContext tc) {