add(coreos-base/oem-cloudstack): CloudStack support

Provide initial support for CloudStack.
eclass: set default portage user and group

The PORTAGE_USERNAME and PORTAGE_GRPNAME variables are not exported by
default. The SDK uses them to get portage to run builds as the
developer's uid/gid instead of portage:portage. When running outside of
the SDK use the default portage user and group.
portage: Add patch to filter EROOT from ebuild environment

EROOT must always be derived from ROOT, preserving it causes binary
packages to break in mysterious and often silent ways.

Upstream: https://bugs.gentoo.org/show_bug.cgi?id=490014
systemd: timesyncd is now enabled under sysinit.target
systemd: re-add support for setting domain name via DHCP
Merge pull request #766 from marineam/time

systemd: timesyncd is now enabled under sysinit.target
app-emulation/docker: bump to 1.1.2
Merge pull request #767 from jonboulle/master

app-emulation/docker: bump to 1.1.2
Merge pull request #757 from marineam/user

eclass: set default portage user and group
Merge pull request #758 from marineam/eroot

portage: Add patch to filter EROOT from ebuild environment
Merge pull request #768 from marineam/domain

systemd: re-add support for setting domain name via DHCP
portage: stabalize 2.2.8
chore(metadata): Regenerate cache
Merge pull request #630 from petrhosek/add-oem-cloudstack

add(coreos-base/oem-cloudstack): CloudStack support
Merge pull request #769 from marineam/portage

Portage 2.2.8 OMG
gmerge: add emerge-gitclone, remove unused scripts
Merge pull request #771 from marineam/gitclone

gmerge: add emerge-gitclone, remove unused scripts
mit-krb5: work around broken autoconf tests

The configure script attempts several tests that cannot be used when
cross compiling. Export the various autoconf vars instead.
Merge pull request #772 from marineam/krb5

mit-krb5: work around broken autoconf tests
bump: fleet v0.6.1