grpc-js-core: more changes

[kjin]

grpc-js-core: unref http2 client socket

The ClientHttp2Session keeps the process alive after all requests are completed; this change works around that.

grpc-js-core: emit status on client stream calls

I think client stream calls are supposed to emit the 'status' event, so I added it here.

grpc-js-core: fixing credentials functions

This change promisifies Http2Channel#connect and makes small changes to credentials-related files to pass the api/credentials_test.js test suite.

grpc-js-core: fixes for interop test

This is a set of changes intended to allow the js client to pass the interop test suite.

[murgatroid99]

Why are these not redundant with the argument type annotations?

[kjin]

TS doesn't auto-generate sentinel checks in JS, its typings are only enforced for other TS files. The credentials test depends on these checks existing, and is written in JS.

[murgatroid99]

Why make options optional here, but not in the implementations?

[kjin]

Whoops -- this was a leftover from some experimentation. I didn't intend to make this optional

[murgatroid99]

The changes to this file do not match the existing implementation, which only emits the status event for calls with response streaming.

[kjin]

It seems like that's not the case -- this test depends on 'status' being emitted for a unary call:

grpc-node/test/api/surface_test.js

Lines 896 to 904 in ac186ec

	it('should be present when a unary call succeeds', function(done) {
	var call = client.unary({error: false}, function(err, data) {
	assert.ifError(err);
	});
	call.on('status', function(status) {
	assert.deepEqual(status.metadata.get('trailer-present'), ['yes']);
	done();
	});
	});

[kjin]

@murgatroid99 PTAL. The only change should be options? to options per your comment.