Improve PR20600 by adding might_sleep() calls in the runtime.

Improve PR20600 by adding might_sleep() calls in the runtime.

* runtime/linux/runtime_context.h (_stp_runtime_entryfn_get_context): Add
  comment about not re-enabling preemption.
* runtime/linux/kprobes.c: Add a few might_sleep() calls.
* runtime/linux/stp_tracepoint.c: Ditto.
* runtime/linux/uprobes-common.c: Ditto.
* runtime/linux/uprobes-inode.c (stapiu_target_lock): Ditto.
* runtime/transport/control.c (_stp_ctl_write_cmd): Ditto.
* runtime/transport/transport.c: Ditto.
* translate.cxx (emit_module_init): Ditto.
* runtime/time.c (_stp_init_time): Ditto.