vSphere support for binary deploys

Aside form working with binary deploys, this PR changes the following two items (vSphere only):

* The reactor on the salt master is configured to run `state.highstate` on *every* node whenever any minion starts. This solves a timing issue introduced with the binary deploys; the master can be done with provisioning much sooner than the minions, meaning the apiserver configuration won't be seeded with the right list of minion IPs. This is solved by running `state.highstate` on minion starts, which causes the apiserver configuration to be rewritten and the daemon to be cycled every time a new minion starts.
* To verify the minions have started from kube-up, the script now polls `http://<ip>:10250/healthz`. The check that is executed from the GCE scripts depends the minions having completed provisioning before the master becomes available. This allows for the case where docker is not yet provisioned, while the master is already responding to requests, which in turn can cause the sanity check to fail.

cc #1732
Probably want to quote `${PUBLIC_KEY_FILE}` here.