appveyor.yml: always publish test results

Our test runner exit code is the number of failures. AppVeyor
misinterprets that as a failed build. Instead of uploading
test results in the "after_test:" phase, upload during the
"on_success:" and "on_failure:" phases (so that the test results
will only but uploaded once, regardless of outcome).

Signed-off-by: Tim Orling <timothy.t.orling@linux.intel.com>