turbonfs: remove GnuTLS dependency, non-TLS only

[pragyagandhi]

Summary

Remove the GnuTLS dependency from the turbonfs build so builds are not blocked on distros
where gnutls is not an allowed package (e.g. Azure Linux). The only supported transport is
non-TLS (xprtsec=none), and AZAUTH (AzAuthNone) is always sent as the first RPC over that
non-TLS connection.

This is the turbonfs/packaging side. The corresponding libnfs changes are in
linuxsmiths/libnfs#39.

Changes

• turbonfs/CMakeLists.txt
  • Drop find_package(GnuTLS) and the static gnutls linking
    (libgnutls/hogweed/nettle/tasn1/idn2/gmp/p11-kit/unistring) — the binary no
    longer links gnutls.
  • Default ENABLE_INSECURE_AUTH_FOR_DEVTEST to ON.
• turbonfs/inc/util.h: is_valid_xprtsec() accepts only none.
• turbonfs/build.sh, package.sh, generate_package.sh: set
  INSECURE_AUTH_FOR_DEVTEST=ON for all build types (not just Debug).

Why the flag is required for all builds

libnfs now has TLS removed, so AZAUTH is always sent over the non-TLS connection. That path is
gated by ENABLE_INSECURE_AUTH_FOR_DEVTEST, and libnfs bails out (static gate) if it is
disabled. Hence turbonfs must enable it for every build type — previously it was Debug-only.

Runtime flow

sequenceDiagram
    participant C as aznfsclient (turbonfs)
    participant L as libnfs
    participant S as Blob NFS server (:2048)
    C->>L: nfs_set_auth_context(authtype=AzAuthNone) -> use_azauth=TRUE
    C->>L: nfs_mount()
    L->>S: TCP connect (non-TLS)
    L->>S: AZAUTH RPC (AzAuthNone)  (always first, over non-TLS)
    alt server has AzAuth enabled
        S-->>L: AZAUTH OK
        L->>S: MOUNT / NFS ops
        S-->>C: mounted (or MNT3ERR_NOENT if container missing)
    else server without AzAuth
        S-->>L: no response / reject
        L-->>C: "AzAuth not enabled/setup on server" diagnostic
    end

Loading

Testing

• Full turbonfs build succeeds; aznfsclient links no gnutls
  (ldd shows only libuuid/libm/libc).
• AzAuth-enabled account: AzAuthNone accepted, proceeds to MOUNT (server responds).
• Non-AzAuth account: AZAUTH fails fast with a clear diagnostic.

Depends on linuxsmiths/libnfs#39 (submodule pointer bump to be done once that merges).