ImageWriter: fix and cleanup the closed Image Handling

Attempting to access an Image after it is closed will result in an ISE.

Also fixed some minor doc issues.

Bug: 19872785
Change-Id: I91f037b2b2f243fcbd905d5a646b505bc9c10638
diff --git a/media/jni/android_media_ImageWriter.cpp b/media/jni/android_media_ImageWriter.cpp
index d2c614e..8c76665 100644
--- a/media/jni/android_media_ImageWriter.cpp
+++ b/media/jni/android_media_ImageWriter.cpp
@@ -338,7 +338,7 @@
     status_t res = anw->dequeueBuffer(anw.get(), &anb, &fenceFd);
     if (res != OK) {
         // TODO: handle different error cases here.
-        ALOGE("%s: Set buffer count failed: %s (%d)", __FUNCTION__, strerror(-res), res);
+        ALOGE("%s: Dequeue buffer failed: %s (%d)", __FUNCTION__, strerror(-res), res);
         jniThrowRuntimeException(env, "dequeue buffer failed");
         return;
     }