relayd: Don't bypass the fd tracker when closing file descriptors

There is no reason to close all file descriptors at this point in the
relay daemon as we know for a fact that the only open fds are stdout
and stderr. If the relayd was to depend on a library that opens other
file descriptors, it would be unadvisable to perform this kind of bulk
closing of all possible file descriptors.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I8ff134094b16dfb6c1aeb875431fdbd4f608eebd