luci-lib-nixio: always build without TLS support

The build system fails to set up the chosen TLS provider and always
builds the package without TLS.

While this could be easily fixed, the package would fail to build with
axTLS and cyaSSL without further intervention.

The version of axTLS included with the source is outdated, as is the API
used with cyaSSL, now wolfSSL.

OpenSSL support could be enabled, but the TLS code limits connections to
TLS 1.0, deprecated by RFC 8996: "TLS 1.0 MUST NOT be used".

Remove the provider configuration from build options, and always build
the library without TLS.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>