Recognize "sandbox" user as indicating automatic testing.

The buildbot slaves actually use "sandbox" as the user name, not "buildbot",
so test for the former instead for the latter, see r73963.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73965 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Enable another test in wxAnyTestCase under OS X.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73966 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775