agent: Simplify agent_popup_message_stop.

* agent/call-pinentry.c (agent_popup_message_stop): Just kill it.

--

By checking if it's alive or not, we can lower a risk of sending
SIGINT to a wrong process on unusual condition when PID is re-used to
a different process.

That's true, however, since it's alive usually, simply sending SIGINT
is enough here.

Note that here is a race condition for detecting if process is active
or not;  A process can die just after being detected alive.

Moreover, when the process of pinentry accidentally died already, it
should have caused return of assuan_transact and the thread of
popup_message_thread likely already set popup_finished=1.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

agent/call-pinentry.c

@@ -1543,14 +1543,6 @@ agent_popup_message_stop (ctrl_t ctrl)
       TerminateProcess (process, 1);
     }
 #else
-  else if (pid && ((rc=waitpid (pid, NULL, WNOHANG))==-1 || (rc == pid)) )
-    { /* The daemon already died.  No need to send a kill.  However
-         because we already waited for the process, we need to tell
-         assuan that it should not wait again (done by
-         unlock_pinentry). */
-      if (rc == pid)
-        assuan_set_flag (entry_ctx, ASSUAN_NO_WAITPID, 1);
-    }
   else if (pid > 0)
     kill (pid, SIGINT);
 #endif