fix(sys-apps/util-linux): Do not exclude the unshare utility.

It is required to run cros_sdk.
fix(coreos-base/coreos-dev): Remove tpm-tools and opencryptoki from dev.

opencryptoki sometimes fails to build by trying to install something to
/var/lock which is a symlink to /run but the SDK makes no promise that
/run is mounted and populated. Instead of fixing the ebuild just drop it
and tpm-tools which depends on it since we don't actually need them.
Merge pull request #176 from marineam/sdk-on-coreos

SDK on CoreOS