Make large uid users run successfully on macOS, fixes #1281

[rfay]

The Problem/Issue/Bug:

A regression in v1.4.0 meant that macOS users (and Linux users, though less likely) with UIDs above 60000 couldn't run ddev successfully (sudo failed, see OP #1281 )

How this PR Solves The Problem:

The basically reverts back to the original behavior, automatically using a uid of 1000 if the UID is above 60000. Otherwise it just tries to use the normal user uid. This is fairly safe on macOS and Windows. It's highly questionable on Linux, where an inappropriate uid can create privileged files.

Manual Testing Instructions:

• Verify correct behavior with a normal lower-numbered uid (ddev ssh and id). The uid and gid should be the same as your macOS uid/gid.
• Create a macOS user with a high UID, say 1553427339. You can do this in system prefs, users and groups. You have to right-click the user for advanced options. I called my user "largeuid"
• Copy the necessary ddev copy to /Users/Shared (or you can download from circleci artifacts)
• Log in with the user
• Start docker
• Make a dummy project and ddev ssh. and id. You should see uid_1000

Automated Testing Overview:

Related Issue Link(s):

Release/Deployment notes:

[andrewfrench]

I was able to ddev start and ddev ssh with a new user, highuid with a user ID of 1553427339. Once in the container, id returned a user id of 1000.