rdbms-sink branch: cancel SQL query when HTTP client disconnects.

[abyrd]

Currently the SQL transaction continues processing after the HTTP client has cancelled its request. It will eventually fail like this:

10:37:39.659 [Grizzly-worker(3)] INFO  c.conveyal.osmlib.PostgresOSMSource - Begin node iteration
Exception in thread "Thread-2" java.lang.RuntimeException: java.io.IOException: Broken pipe
        at com.conveyal.osmlib.PBFOutput.writeOneBlob(PBFOutput.java:116)
        at com.conveyal.osmlib.PBFOutput.run(PBFOutput.java:308)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: Broken pipe
        at sun.nio.ch.FileDispatcherImpl.write0(Native Method)
        at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:47)
        at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93)
        at sun.nio.ch.IOUtil.write(IOUtil.java:51)
        at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:471)
        at org.glassfish.grizzly.nio.transport.TCPNIOUtils.flushByteBuffer(TCPNIOUtils.java:149)
        at org.glassfish.grizzly.nio.transport.TCPNIOUtils.writeCompositeBuffer(TCPNIOUtils.java:87)
        at org.glassfish.grizzly.nio.transport.TCPNIOAsyncQueueWriter.write0(TCPNIOAsyncQueueWriter.java:112)
        at org.glassfish.grizzly.nio.transport.TCPNIOAsyncQueueWriter.write0(TCPNIOAsyncQueueWriter.java:91)
        at org.glassfish.grizzly.nio.AbstractNIOAsyncQueueWriter.write(AbstractNIOAsyncQueueWriter.java:261)
        at org.glassfish.grizzly.nio.AbstractNIOAsyncQueueWriter.write(AbstractNIOAsyncQueueWriter.java:170)
        at org.glassfish.grizzly.nio.AbstractNIOAsyncQueueWriter.write(AbstractNIOAsyncQueueWriter.java:70)
        at org.glassfish.grizzly.nio.transport.TCPNIOTransportFilter.handleWrite(TCPNIOTransportFilter.java:126)
        at org.glassfish.grizzly.filterchain.TransportFilter.handleWrite(TransportFilter.java:191)
        at org.glassfish.grizzly.filterchain.ExecutorResolver$8.execute(ExecutorResolver.java:111)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
        at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
        at org.glassfish.grizzly.filterchain.FilterChainContext.write(FilterChainContext.java:848)
        at org.glassfish.grizzly.filterchain.FilterChainContext.write(FilterChainContext.java:817)
        at org.glassfish.grizzly.http.io.OutputBuffer.flushBuffer(OutputBuffer.java:1024)
        at org.glassfish.grizzly.http.io.OutputBuffer.write(OutputBuffer.java:680)
        at org.glassfish.grizzly.http.io.OutputBuffer.write(OutputBuffer.java:542)
        at org.glassfish.grizzly.http.server.NIOOutputStreamImpl.write(NIOOutputStreamImpl.java:75)
        at com.conveyal.osmlib.PBFOutput.writeOneBlob(PBFOutput.java:114)
        ... 2 more