enable-os-refresh-update config option causes bootstrap to take significantly longer than without it.

[Ryan Beisner]

Use of the "enable-os-refresh-update" config option causes bootstrap to take significantly longer than without it. 21 minutes vs 2 minutes in my case.

In a bit of irony, I started using this option for faster machine provisioning as indicated is possible in the docs:
https://jujucharms.com/docs/2.1/models-config#apt-updates-and-upgrades-with-faster-machine-provisioning

With, and without the config option specified, the controller machine instance is ready and accessible within 2 minutes. In the case where the config option is set true, there is nothing bound to tcp socket 17070 until the final moments of bootstrap success, confirmed by watching `sudo netstat -taupn` on the controller instance.

## Reproducer:
#### Without the option
time juju bootstrap --bootstrap-constraints 'virt-type=kvm cores=4 mem=8G' serverstack/serverstack beisner-serverstack

#### With the option
time juju bootstrap --bootstrap-constraints 'virt-type=kvm cores=4 mem=8G' --config enable-os-refresh-update=false serverstack/serverstack beisner-serverstack

## Reproducer Output:
#### Without the option (2 min)
ubuntu@beisner-bastion:~/git/charm-test-infra⟫ time juju bootstrap --bootstrap-constraints 'virt-type=kvm cores=4 mem=8G' serverstack/serverstack beisner-serverstack
Creating Juju controller "beisner-serverstack" on serverstack/serverstack
Looking for packaged Juju agent version 2.1.2 for amd64
Launching controller instance(s) on serverstack/serverstack...
 - 85f4404f-27fd-49a1-aaae-7378e1b651b9 (arch=amd64 mem=8G cores=4)
Fetching Juju GUI 2.5.2
Waiting for address
Attempting to connect to 10.5.0.9:22
Warning: Permanently added '10.5.0.9' (ECDSA) to the list of known hosts.
sudo: unable to resolve host juju-ab1b24-controller-0
Logging to /var/log/cloud-init-output.log on the bootstrap machine
Running apt-get update
Running apt-get upgrade
Installing curl, cpu-checker, bridge-utils, cloud-utils, tmux
Fetching Juju agent version 2.1.2 for amd64
Installing Juju machine agent
Starting Juju machine agent (service jujud-machine-0)
Bootstrap agent now started
Contacting Juju controller at 10.5.0.9 to verify accessibility...
Bootstrap complete, "beisner-serverstack" controller now available.
Controller machines are in the "controller" model.
Initial model "default" added.

real 2m0.794s
user 0m1.256s
sys 0m0.080s

## Reproducer Output:
#### With the option (21 min)
130 ubuntu@beisner-bastion:~/git/charm-test-infra⟫ time juju bootstrap --bootstrap-constraints 'virt-type=kvm cores=4 mem=8G' --config enable-os-refresh-update=false serverstack/serverstack beisner-serverstack
Creating Juju controller "beisner-serverstack" on serverstack/serverstack
Looking for packaged Juju agent version 2.1.2 for amd64
Launching controller instance(s) on serverstack/serverstack...
 - 2fb722cf-dd55-406f-b701-ac7e8dc951f0 (arch=amd64 mem=8G cores=4)
Fetching Juju GUI 2.5.2
Waiting for address
Attempting to connect to 10.5.0.13:22
Warning: Permanently added '10.5.0.13' (ECDSA) to the list of known hosts.
sudo: unable to resolve host juju-8873d0-controller-0
Logging to /var/log/cloud-init-output.log on the bootstrap machine
Running apt-get upgrade
Installing curl, cpu-checker, bridge-utils, cloud-utils, tmux

Fetching Juju agent version 2.1.2 for amd64
Installing Juju machine agent
Starting Juju machine agent (service jujud-machine-0)
Bootstrap agent now started
Contacting Juju controller at 10.5.0.13 to verify accessibility...
Bootstrap complete, "beisner-serverstack" controller now available.
Controller machines are in the "controller" model.
Initial model "default" added.

real 21m43.145s
user 0m1.780s
sys 0m0.132s

[Ian Booth (wallyworld)]

It would be very useful to see the cloud-init.log and cloud-init-output.log files from both scenarios. This will tell us exactly what apt related update settings got passed through to cloud-init, and how cloud-init reacted to those. Both of these should be available in /var/log/cloud-init

[Launchpad Janitor (janitor)]

[Expired for juju because there has been no activity for 60 days.]