Remove OPENSSL_USE_NODELETE guards in shlibloadtest

PR #3399 converted shlibloadtest to the new test framework. It also
seemed to add some `OPENSSL_USE_NODELETE` guards to the library
unloading part of the test. This part was added in a commit with this
description:

    Review feedback; use single main, #ifdef ADD_TEST

    Suppose OPENSSL_USE_NODELETE (via Nick Reilly)

Strangely though there doesn't seem to be any relevant review feedback
in that PR that could justify the addition of those guards. The guards
do not appear in 1.1.0.

Having the guards changes the nature of the test, so that we only test
library unloading on platforms where OPENSSL_USE_NODELETE is set (Linux
and Windows). I can't think of any good reason for this and as it doesn't
seem to be necessary in 1.1.0 so I think we should remove them.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5530)