BUG/MINOR: httpclient: end callback in applet release

In case an error provokes the release of the applet, we will never call
the end callback of the httpclient.

In the case of a lua script, it would mean that the lua task will never
be waked up after a yield, letting the lua script stuck forever.

Fix the issue by moving the callback from the end of the iohandler to
the applet release function.

Must be backported in 2.5.
1 file changed