[cache] Fix concurrent use of a cache entry (#3785)

Closes #3507
Fix some rare case where the concurrent readings of a cache entry can fail.

Signed-off-by: Gwendal Roulleau <gwendal.roulleau@gmail.com>

bundles/org.openhab.core/src/main/java/org/openhab/core/cache/lru/LRUMediaCacheEntry.java

@@ -296,7 +296,7 @@ public class LRUMediaCacheEntry<V> {
             }
         }
         // the cache file is now filled, get bytes from it.
-        long maxToRead = Math.min(currentSize, sizeToRead);
+        long maxToRead = Math.min(fileChannelLocal.size(), sizeToRead);
         ByteBuffer byteBufferFromChannelFile = ByteBuffer.allocate((int) maxToRead);
         int byteReadNumber = fileChannelLocal.read(byteBufferFromChannelFile, Integer.valueOf(start).longValue());
         logger.trace("Read {} bytes from the filechannel", byteReadNumber);