profiles: disable calling sync(2) after installing packages

This is just a safety feature for real Gentoo systems on the off chance
that they crash moments after a package is installed. There isn't any
such concern for the CoreOS SDK so just disable it. A normal build_image
is slightly faster with this but I suspect it may help the build host
which is usually running many emerge jobs in parallel.
coreos-kernel: enable dummy ethernet driver
coreos-kernel: prune old 3.14.x versions
systemd: remove timesyncd symlink from /etc

Along with the other services systemd is enabling in /etc the built in
SNTP client has been added to. Unlike the others we don't re-enable it
in /usr since we are currently using ntpd instead.
coreos-base/coreos-cloudinit: bump to v0.8.2
Merge pull request #713 from marineam/systemd

systemd: remove timesyncd symlink from /etc
Merge pull request #711 from marineam/dummy

Enable dummy ethernet driver
Merge pull request #709 from marineam/nosync

profiles: disable calling sync(2) after installing packages
Merge pull request #714 from crawford/cloudinit

coreos-base/coreos-cloudinit: bump to v0.8.2
coreos-base/coreos-cloudinit: bump to v0.8.3
Merge pull request #715 from crawford/master

coreos-base/coreos-cloudinit: bump to v0.8.3
coreos-init: remove default coreos-setup-environment

The coreos-setup-environment script can now only be provided by OEMs,
the default script that used to run when the OEM didn't provide one was
not smart enough to wait for networking to be configured before writing
out /etc/environment *but* we cannot simply add such a wait because that
would make it impossible for users to use cloud config in configdrive or
similar to configure static networking.

Longer term coreos-cloudinit will replace at least some of the current
OEM coreos-setup-environment scripts and perhaps eventually integrate
with networkd to cover the default case reasonably well. Sorting this
out is still ongoing.

(This ebuild bump was supposed to land a week ago but we missed it.)
Merge pull request #717 from marineam/init

coreos-init: remove default coreos-setup-environment
coreos-base/coreos-cloudinit: bump to v0.8.6
Merge pull request #718 from crawford/master

coreos-base/coreos-cloudinit: bump to v0.8.6
Revert "oem-ec2-compat: Check for metadata service and config drive"

The functionality for this in cloudinit 0.8.x is broken.

This reverts commit 91cc8446212c6b35c80cbdbbc204a9fe3cd1f756.
coreos-cloudinit: roll back to 0.7.7, the 0.8.x series still needs work.
Merge pull request #716 from marineam/rollback

Rollback to last working cloudinit
coreos-cloudinit: roll forward to 0.8.6

We may have the last of the issues sorted...

This reverts commit b34d0a3308 and 20aa920e7f.
oem-ec2-compat: remove dependency on coreos-setup-environment

The coreos-setup-environment no longer generates /etc/environment on
systems using this OEM package so remove the requirement.