dhcpcd: backport two patches to fix runtime error

In case of nodistro, dhcpcd gives us 'Bad system call'
error and exits. This is because there are syscalls that
should be allowed but not in privsep. Backport two patches
to fix this issue.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit f1e6a0c1)
Signed-off-by: Steve Sakoman <steve@sakoman.com>