test: scale keepAliveTimeoutBuffer with platformTimeout

Author: geeksilva97

test/sequential/test-http-server-keep-alive-timeout-slow-client-headers.js

@@ -10,6 +10,7 @@ const server = http.createServer(common.mustCall((req, res) => {
 }, 2));
 
 server.keepAliveTimeout = common.platformTimeout(100);
+server.keepAliveTimeoutBuffer = common.platformTimeout(1000);
 
 server.listen(0, common.mustCall(() => {
   const port = server.address().port;

test/sequential/test-http-server-keep-alive-timeout-slow-server.js

@@ -15,6 +15,7 @@ const server = http.createServer(common.mustCall((req, res) => {
 }, 2));
 
 server.keepAliveTimeout = common.platformTimeout(200);
+server.keepAliveTimeoutBuffer = common.platformTimeout(1000);
 
 const agent = new http.Agent({
   keepAlive: true,