fixed memory leak in InMemoryCache

gbcs-common/src/main/kotlin/net/woggioni/gbcs/common/ByteBufOutputStream.kt

@@ -0,0 +1,19 @@
+package net.woggioni.gbcs.common
+
+import io.netty.buffer.ByteBuf
+import java.io.InputStream
+import java.io.OutputStream
+
+class ByteBufOutputStream(private val buf : ByteBuf) : OutputStream() {
+    override fun write(b: Int) {
+        buf.writeByte(b)
+    }
+
+    override fun write(b: ByteArray, off: Int, len: Int) {
+        buf.writeBytes(b, off, len)
+    }
+
+    override fun close() {
+        buf.release()
+    }
+}