Fix incorrect TAP test ordering

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