Add javax.websocket to pom.xml

[jsoref]

IntelliJ configured to use adoptopenjdk openj9 1.8 complains about:

remoting/src/main/java/hudson/remoting/Engine.java

Lines 70 to 76 in ca2fbc6

	import javax.websocket.ClientEndpointConfig;
	import javax.websocket.CloseReason;
	import javax.websocket.ContainerProvider;
	import javax.websocket.Endpoint;
	import javax.websocket.EndpointConfig;
	import javax.websocket.HandshakeResponse;
	import javax.websocket.Session;

This appears to make it happy.

[jeffret-b]

It seems to work fine. I'm a little concerned about adding a dependency if it isn't needed but I don't see how it causes a problem either. I've played around with testing it a little and don't see that this changes anything. It does make more sense that it be listed as a dependency as it is imported.

[jeffret-b]

I'm not sure that makes a real difference but that's better to specify the scope.