feat(dev-db/etcd): run as etcd user

thie patch does a few things

1) Add the etcd user and run etcd as that user

2) Add the /var/lib/etcd directory and have it owned by the etcd user

3) Move /media/state/etcd/* files into /var/lib/etcd/ and chown them to
   etcd

Test-plan: Build an AMI and ensure this all works with the
bootstrapping.
fix(dev-db/etcd): use new state location

have etcd use /var/lib like other daemons do.
fix(dev-db/etcd): use mkdir -p in pre-exec

Ensure that we don't fail on the /var/run/etcd directory creation.
Merge pull request #141 from philips/etcd-restrictions

feat(dev-db/etcd): run as etcd user