MEDIUM: mux-h1: use task_kill() during h1_takeover() instead of task_wakeup()

MEDIUM: mux-h1: use task_kill() during h1_takeover() instead of task_wakeup()

task_wakeup() passes the task through the global run queue under the
global RQ lock, which is expensive when dealing with large amounts of
h1_takeover() calls. Let's use the new task_kill() instead to kill the
task.

By doing so, a scenario involving approximately 130k takeover/s running on
16 threads gained almost 3% performance from 319k req/s to 328k.