files: Handle eventpoll files deferred

Since event polling depends on other files
to be opened we split main files list into
two parst -- event poll files and all other
files, thus defer the creation of eventpoll
files in prepare_fds().

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>