Rackspace - Switch to CoreOS for standard cluster

The Rackspace setup for Kubernetes now leverages CoreOS instead of Ubuntu. We've dropped Salt completely for our cluster.

(cherry picked from commit a8bae68865a5f87e5ba52fe6a331714940d48587)
Add Rackspace to build/release.sh

Updates to the build/release.sh scripts to upload build binaries to
Cloud Files.

(cherry picked from commit f2838483a137507c5b56c10222c35005d53ca7fa)
remove hardcoded cloudfiles path and fix PORTAL_NET

(cherry picked from commit 0bfb5ae772ce17b165c4445505b54b9cbcd31f70)
Migrate Rackspace upload scripts to util.sh

The functions to upload built k8s tars to Cloud Files were incorrectly
placed in build/common.sh. These have been migrated to
cluster/rackspace/util.sh

(cherry picked from commit a26aefaa2ee32af907a4a0b29dea07a5679e44de)
Remove extra newline and update comments in util.sh

(cherry picked from commit d513854851bff0aeb78bf972019900c71b29172b)
Fix boot2docker with /User mapping.

Fixes #1856

Based on #1858 from @nyaxt.

(cherry picked from commit e48cbb2296369869bb8d3517f6a7e769b1dc0a6f)

Conflicts:
	build/common.sh
Do not require a writeable /vagrant

(cherry picked from commit 0d86be680b318225d5129cdddd48c64d1bdc42de)
Turn on auto security updates for debian based systems.

Fixes #2008

(cherry picked from commit 8100c063b8eecf0e404959c6cd595ac81a1aa0bb)