Fix ENGINE support with OpenSSL 1.1+

Fix ENGINE support with OpenSSL 1.1+

Commit 373c7969485 ("OpenSSL: Fix compile with OpenSSL 1.1.0 and
deprecated APIs") removed a call to ENGINE_load_dynamic() for newer
versions of OpenSSL, asserting that it should happen automatically.

That appears not to be the case, and loading engines now fails because
the dynamic engine isn't present.

Fix it by calling ENGINE_load_builtin_engines(), which works for all
versions of OpenSSL. Also remove the call to ERR_load_ENGINE_strings()
because that should have happened when SSL_load_error_strings() is
called anyway.

Fixes: 373c79694859 ("OpenSSL: Fix compile with OpenSSL 1.1.0 and deprecated APIs")
Signed-off-by: David Woodhouse <dwmw2@infradead.org>