* caddyhttp: Honor grace period in background
This avoids blocking during config reloads.
* Don't quit process until servers shut down
* Make tests more likely to pass on fast CI (#5045)
* caddyhttp: Even faster shutdowns
Simultaneously shut down all HTTP servers, rather than one at a time.
In practice there usually won't be more than 1 that lingers. But this
code ensures that they all Shutdown() in their own goroutine
and then we wait for them at the end (if exiting).
We also wait for them to start up so we can be fairly confident the
shutdowns have begun; i.e. old servers no longer
accepting new connections.
* Fix comment typo
* Pull functions out of loop, for readability
* reverse proxy: Support more h2 stream scenarios (#3556)
* reverse proxy: add integration test for better h2 stream (#3556)
* reverse proxy: adjust comments as francislavoie suggests
* link to issue #3556 in the comments
