selftests: net: fcnal-test: check if FIPS mode is enabled

There are some MD5 tests which fail when the kernel is in FIPS mode,
since MD5 is not FIPS compliant. Add a check and only run those tests
if FIPS mode is not enabled.

Fixes: f0bee1eb ("fcnal-test: Add TCP MD5 tests")
Fixes: 5cad8bce ("fcnal-test: Add TCP MD5 tests for VRF")
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Magali Lemes <magali.lemes@canonical.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>