fix warning unused-but-set-variable 'nostrict' (no-dh and no-ec)

This patch fixes the following warning when OpenSSL is configured with
no-dh and no-ec:

./Configure no-ec no-dh linux-x86_64

...
s3_lib.c:4231:9: warning: variable 'nostrict' set but not used [-Wunused-but-set-variable]
     int nostrict = 1;
         ^

CLA: trivial
Signed-off-by: Cristian Stoica <cristian.stoica@nxp.com>

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6087)