xds: fix ServerXdsClient to return subscribed resources only for LDS

[sanjaypujare]

No description provided.

[voidzcy]

Some comment on other small issues in ServerXdsClient code. They are not related to this PR, most of them should be cosmetic things:

• nit: these parentheses are redundant.
  

  grpc-java/xds/src/main/java/io/grpc/xds/ServerXdsClient.java

  Lines 70 to 72 in 8f6813f

  	this.instanceIp = (instanceIp != null ? instanceIp : "0.0.0.0");
  	this.grpcServerResourceId =
  	(grpcServerResourceId != null) ? grpcServerResourceId : "grpc/server";

grpc-java/xds/src/main/java/io/grpc/xds/ServerXdsClient.java

Line 191 in 8f6813f

return address.hasSocketAddress() && (address.getSocketAddress().getPortValue() == portToMatch);

• The field name newServerApi is not informative. It doesn't say imply anything useful.

• The following small chunk of code involves 3-4 indirections of calling helper methods. There is very little code reuse involved while logics are fragmented into multiple pieces. It's a pretty bad review experience. It could be refactored and condensed.

grpc-java/xds/src/main/java/io/grpc/xds/ServerXdsClient.java

Lines 180 to 204 in 8f6813f

	private boolean isRequestedListener(Listener listener) {
	if (newServerApi) {
	return grpcServerResourceId.equals(listener.getName())
	&& listener.getTrafficDirection().equals(TrafficDirection.INBOUND)
	&& isAddressMatching(listener.getAddress(), listenerPort);
	}
	return isAddressMatching(listener.getAddress(), 15001)
	&& hasMatchingFilter(listener.getFilterChainsList());
	}
	private boolean isAddressMatching(Address address, int portToMatch) {
	return address.hasSocketAddress() && (address.getSocketAddress().getPortValue() == portToMatch);
	}
	private boolean hasMatchingFilter(List<FilterChain> filterChainsList) {
	// TODO(sanjaypujare): if myIp to be checked against filterChainMatch.getPrefixRangesList()
	for (FilterChain filterChain : filterChainsList) {
	FilterChainMatch filterChainMatch = filterChain.getFilterChainMatch();
	if (listenerPort == filterChainMatch.getDestinationPort().getValue()) {
	return true;
	}
	}
	return false;
	}

• The following indentation looks wrong:
  

  grpc-java/xds/src/main/java/io/grpc/xds/ServerXdsClient.java

  Lines 183 to 184 in 8f6813f

  	&& listener.getTrafficDirection().equals(TrafficDirection.INBOUND)
  	&& isAddressMatching(listener.getAddress(), listenerPort);

[sanjaypujare]

Some comment on other small issues in ServerXdsClient code. They are not related to this PR, most of them should be cosmetic things:

Probably valid comments and I'll fix some. Note that the newServerApi variable is going to go away and all the code for newServerApi == false is going to go away once TD code is in prod and tested. So not spending time to address those comments

[voidzcy]

Well, the two copies of tests have already diverged. But it is minor...