Fix incorrect TAP test ordering
Using a test function before a possible skip_all is incorrect. If the
skip_all is called, the test output will become incorrect and the test
file will fail.
a4f23f9b3c introduced a new test before skip_all. After discussion,
this doesn't really need to be a test. Instead, we just bail out if
the condition is not satisfied.
Discussion: https://www.postgresql.org/message-id/
af5567a1-aea6-fbdb-7e4b-
d1e23a43c43b@enterprisedb.com