stdio-bridge: fix polled fds

Poll fds associated with the bus instead of hardcoding stdin/stdout.

This is consequential under socket activation, when the provided fd
should be used instead of stdin/stdout.

(cherry picked from commit 9d1c28b)
(cherry picked from commit 59f5a4323468befbdca2bae7907219eaf8852f9a)
(cherry picked from commit a398d18)
(cherry picked from commit 0ae29e6)
(cherry picked from commit fb92304)
(cherry picked from commit eab1d97)
(cherry picked from commit daa7763)

Author: jacobmcnamee

src/stdio-bridge/stdio-bridge.c

@@ -244,9 +244,9 @@ static int run(int argc, char *argv[]) {
                 t = usec_sub_unsigned(MIN(timeout_a, timeout_b), now(CLOCK_MONOTONIC));
 
                 struct pollfd p[3] = {
-                        { .fd = fd,            .events = events_a           },
-                        { .fd = STDIN_FILENO,  .events = events_b & POLLIN  },
-                        { .fd = STDOUT_FILENO, .events = events_b & POLLOUT },
+                        { .fd = fd,     .events = events_a           },
+                        { .fd = in_fd,  .events = events_b & POLLIN  },
+                        { .fd = out_fd, .events = events_b & POLLOUT },
                 };
 
                 r = ppoll_usec(p, ELEMENTSOF(p), t);