Ddev: Prepare/test for macOS Big Sur release

[rfay]

We need to make sure that ddev works on macOS Big Sur when it comes out, and can succeed running all tests, etc.

• [x] Basic functionality of ddev
• [x] ddev with NFS, basic functionality
• [x] Run full test suite

[rfay]

At this point, I have a recurring docker bug that causes a full system crash, after which Docker can't start.

[rfay]

The crash full-on system crash occurs every time you do a ddev start when using NFS. It has been reported via slack to the Docker desktop team, https://dockercommunity.slack.com/archives/G013121J9RN/p1599748088025500?thread_ts=1599166573.012100&cid=G013121J9RN

1. Configure NFS as described in https://ddev.readthedocs.io/en/stable/users/performance/ (it's easy, just run the script linked)
2. Install ddev (brew tap drud/ddev && brew install ddev)
   3 mkdir junk && cd junk
3. ddev config --nfs-mount-enabled
4. ddev start

Immediate system crash, after which docker won't start, factory defaults reset is required. (Sometimes even that won't do it)

Docker seems to work OK without nfs-mount-enabled.

[rfay]

The crash appears to be a macOS Big Sur bug with NFS, see https://www.reddit.com/r/MacOSBeta/comments/ij84h6/nfs_server_bug_in_macos_11_big_sur_beta_5/

The bug still appears in beta6. I'm downloading beta7, which was released today.

[rfay]

The nfs crash is fixed in beta7, yay!

[rfay]

Most of the test suite is working. I had to move the testdir to within homedir instead of /tmp (/var/folders) in #2516, but that's a good thing. It's better there, and the test runner setup is easier.

• TestConfigValidate fails, but not when run by itself, must be interaction with another test
• TestShareCmd fails if ngrok was just installed and not right-click opened. It pops up the complaint that it's from an unidentified developer if you brew cask install ngrok and that's it. But just right-clicking and saying open anyway fixes it.

[rfay]

I've had at least one manual full test run, so calling this good for now. I have suspicions about some intermittent trouble with Docker edge.