Fix log skip condition

[yohsuke]

I think that 2nd "!" of these should not be. These javadoc says, "log-if-not-isExpected", but the code is "nothing-if-not-isExpected".

[Background]

In some service, too many "Connection reset" exceptions like below are logged after version up the armeria (0.8.0.Final -> 0.9.0.Final).

It may be the effect of #105 (released in 0.9.0.Final)

2016-03-03 18:10:36.424 WARN  nioEventLoopGroup-7-6 com.linecorp.armeria.server.HttpServerHandler:53 - [id: 0x648cec6b, L:/XX.XX.XX.XX:20012 - R:/YY.YY.YY.YY:30664] Unexpected exception:
java.io.IOException: Connection reset by peer
        at sun.nio.ch.FileDispatcherImpl.read0(Native Method) ~[na:1.8.0_66]
        at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39) ~[na:1.8.0_66]
        at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223) ~[na:1.8.0_66]
        at sun.nio.ch.IOUtil.read(IOUtil.java:192) ~[na:1.8.0_66]
        at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380) ~[na:1.8.0_66]
        at io.netty.buffer.PooledUnsafeDirectByteBuf.setBytes(PooledUnsafeDirectByteBuf.java:288) ~[beacon-lineapi.jar:na]
        at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1055) ~[beacon-lineapi.jar:na]
        at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:245) ~[beacon-lineapi.jar:na]
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:112) ~[beacon-lineapi.jar:na]
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:510) [beacon-lineapi.jar:na]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:467) [beacon-lineapi.jar:na]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:381) [beacon-lineapi.jar:na]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:353) [beacon-lineapi.jar:na]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:742) [beacon-lineapi.jar:na]
        at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137) [beacon-lineapi.jar:na]
        at java.lang.Thread.run(Thread.java:745) [na:1.8.0_66]

[trustin]

@yohsuke Thanks a lot!