alternator: use has_function instead of try-catch
alternator: use has_function instead of try-catch

With the new interface available, the try-catch idiom
can be removed, thus resolving a TODO.

Tests: unit(dev)

Message-Id: <1753f65f75ed007930c63bb919d0d44854e341d0@scylladb.com>

avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla