http2-io: explicitly call check_status when switching to STATE_READ_DATA on stream end

Also make sure we only call check_status for async requests.
7 jobs for master in 4 minutes and 46 seconds
Status Job ID Name Coverage
  Build
passed fedora-asan #1340818
asan

00:03:02

passed fedora-autobahn-quick #1340816
ipv6

00:04:46

passed fedora-scan #1340817
ipv6

00:01:57

passed fedora-test #1340815
ipv6

00:02:04

83.9%
 
  Docs
passed reference #1340819

00:00:44

 
  Deploy
passed pages #1340820

00:00:46

passed pages:deploy

00:00:01