ftp/curl: Specify default CA path

Add --with-ca-path=/etc/ssl/certs to CONFIGURE_ARGS so GnuTLS and wolfSSL can
find CA certificates by default.

Remove --with-ca-fallback. It has no effect with GnuTLS and with OpenSSL curl
uses the OpenSSL CA path which should also be /etc/ssl/certs so it is redundant
now.

PR: 288861, 288862