ueventd: fix a busy loop while reading uevents

Under certain conditions, poll() may raise the POLLERR
flag along with POLLIN, in which case the check for
(ufd.revents == POLLIN) results in an endless busy loop.

The following fix was applied to
hardware/libhardware_legacy/uevent/uevent.c
to fix a similar bug:

  commit 3aabb260ceef10377c31c9e45fb239247f5cfeba
  Author: Mathias Agopian <mathias@google.com>
  Date:   Mon Oct 1 14:53:18 2012 -0700

    fix a typo in uevent_next_eventi

    Bug: 7114973
    Change-Id: I15a4c714b59aeb1d02db00517d70b5f0e5ab22c2

Applying the same fix for two more poll loops in init
and ueventd.

Change-Id: I50693f6d3c904992ac4b8a9a14a83c7106e6b9e0