tests,fips: Align the use of variable in_fips_mode.

* tests/pubkey.c (check_run): Fix use of pkey and skey.
* tests/*.c (in_fips_mode): No initialize by 0.

There are no cases where *_key_new allocates pkey and skey when
IN_FIPS_MODE!=0. Nevertheless, from viewpoint of resource management,
calling gcry_sexp_release always is easier for maintenance.

• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>