Follow-on to #7337. Been seeing other CI test failures that point to
these temp directories, so let's just move all of them to /tmp. I'm sure
someone will write ext2fs stress tests later :^)
Example:
/usr/Tests/Shell/control-structure-as-command.sh
Core::Socket: Failed to connect() to /tmp/portal/inspectables: ...
+ rm -rf shell-test 2>/dev/null
+ mkdir shell-test
Error: The action has timed out.
There's no guarantee that the last executed command will have a zero
exit code, and so the shell exit code may or may not be zero, even if
all the tests pass.
Also changes the `test || echo fail && exit` to
`if not test { echo fail && exit }`, since that's nicer-looking.
