salt-cloud map partial rebuild doesn't distribute minion keys to master

Description of Issue/Question

We have a situation where we're using map files and salt-cloud to create environments of several virtual machines in Proxmox. The complete environment build works as expected. The environments include an ESM (Environment Salt Master) and in the initial build this all works fine - salt-cloud generates minion keys for all of the minions and distributes them to the ESM.

However, if we destroy one of the machines in order to rebuild it and use salt-cloud to rebuild we hit a few problems.

1. The hostname for the ESM cannot be figured out with the current code. I can work around that (I don't really understand yet what that part of the code is meant to be doing in order to get the hostname btw)

2. New minion keys are generated for the missing server, but the server build fails because the ESM rejects the minion's key. This is because salt-cloud doesn't

I can't work around 2. - Does anyone else have this problem, or know a way round this issue?

Setup

A reasonably complex map file.

Steps to Reproduce Issue

Use salt-cloud with a valid map that contains an ESM (environment salt master).
Build the environment successfully.
Terminate one of the VMs
Re-build the environment and salt-cloud will fail as described above.

Versions Report

Salt Version:
           Salt: 2018.11.0-6301-g0a5d2de
 
Dependency Versions:
           cffi: 1.11.5
       cherrypy: Not Installed
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
         Jinja2: 2.10
        libgit2: Not Installed
       M2Crypto: 0.28.2
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.6.1
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.5 (default, Oct 30 2018, 23:45:53)
   python-gnupg: Not Installed
         PyYAML: 3.13
          PyZMQ: 18.0.0
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.3.1
 
System Versions:
           dist: centos 7.6.1810 Core
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-957.5.1.el7.x86_64
         system: Linux
        version: CentOS Linux 7.6.1810 Core

Start by reproducing the partial rebuild with the salt-cloud map described in the issue, then trace how the ESM hostname and newly generated minion keys are handled. Done means the rebuilt VM's key is distributed to and accepted by the ESM during the map rebuild.