test: http2 compat response.write() error checks

[trivikr]

This code change adds tests for the following code:

node/lib/internal/http2/compat.js

Lines 541 to 553 in 472cde6

	if(typeofencoding==='function'){
	cb=encoding;
	encoding='utf8';
	}
	if(this[kState].closed){
	consterr=newerrors.Error('ERR_HTTP2_INVALID_STREAM');
	if(typeofcb==='function')
	process.nextTick(cb,err);
	else
	throwerr;
	return;
	}

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

http2

[jasnell]

LGTM so long as CI comes back green

[jasnell]

CI: https://ci.nodejs.org/job/node-test-pull-request/13288/

[BridgeAR]

Landed in a926c1a 🎉