tests/basic: Skip non-FIPS tests in FIPS mode

* tests/basic.c (check_pubkey): Skip non-FIPS tests in FIPS mode, fixes
  a logic error previously introduced in e9698002.

e96980022e5ec079c9d4e3492eb6a1131c68e0f2 did change the behavior of
tests/basic.c to actually run non-FIPS tests in FIPS mode because the
'continue' statement was moved into the else block.

This fails when libgcrypt is configured, for example, without support
for RSA.

• GnuPG-bug-id: T6048
• Signed-off-by: Clemens Lang <cllang@redhat.com>