juju upgrade-juju fails on model if juju upgrade-juju -m controller run first instead of juju upgrade-controller

[Heather Lanigan]

Steps to reproduce and resolve.

$ /snap/bin/juju upgrade-juju -m controller
best version:
    2.6.1
started upgrade to 2.6.1
$ /snap/bin/juju status -m controller
Model Controller Cloud/Region Version SLA Timestamp
controller testme localhost/localhost 2.6.1 unsupported 10:32:09-04:00

Machine State DNS Inst id Series AZ Message
0 started 10.121.191.56 juju-cef1ae-0 bionic Running
$ /snap/bin/juju upgrade-juju
best version:
    2.6.1
ERROR model cannot be upgraded to 2.6.1 while the controller is 2.5.4: upgrade 'controller' model first
$ /snap/bin/juju upgrade-juju -m controller
no upgrades available
$ /snap/bin/juju upgrade-juju
best version:
    2.6.1
ERROR model cannot be upgraded to 2.6.1 while the controller is 2.5.4: upgrade 'controller' model first
$ /snap/bin/juju version
2.6.1-disco-amd64
$ /snap/bin/juju status -m controller
Model Controller Cloud/Region Version SLA Timestamp
controller testme localhost/localhost 2.6.1 unsupported 10:35:53-04:00

Machine State DNS Inst id Series AZ Message
0 started 10.121.191.56 juju-cef1ae-0 bionic Running

$ /snap/bin/juju upgrade-controller
no upgrades available
$ /snap/bin/juju upgrade-juju -m default
best version:
    2.6.1
started upgrade to 2.6.1

[Heather Lanigan (hmlanigan)]

something must have been slow - no longer reproducible.