fw/target: fix signals reboot on unresponsive

- Add "hard" parameter to TargetManager's reboot().
- Pass in context to TargetManager's reboot() and
  verify_target_responsive() -- this is needed for signal dispatch.
- Call self.reboot() instead of self.target.reboot() when attempting a
  reset for unresponsive targets inside TargetManager, in order to
  ensure that appropriate signals are dispatched.

wa/framework/instrument.py

@@ -259,7 +259,7 @@ class ManagedCallback(object):
                 if isinstance(e, WorkloadError):
                     context.set_status('FAILED')
                 elif isinstance(e, TargetError) or isinstance(e, TimeoutError):
-                    context.tm.verify_target_responsive(context.reboot_policy.can_reboot)
+                    context.tm.verify_target_responsive(context)
                 else:
                     if context.current_job:
                         context.set_status('PARTIAL')