Merge branch 'jk/sanity' into maint
The tests that wanted to see that file becomes unreadable after
running "chmod a-r file", and the tests that wanted to make sure it
is not run as root, we used "can we write into the / directory?" as
a cheap substitute, but on some platforms that is not a good
heuristics. The tests and their prerequisites have been updated to
check what they really require.
* jk/sanity:
test-lib.sh: set prerequisite SANITY by testing what we really need
tests: correct misuses of POSIXPERM
t/lib-httpd: switch SANITY check for NOT_ROOT