ctdb-daemon: Drop ctdbd --socket option

ctdb-daemon: Drop ctdbd --socket option

Use environment variables for test-only options.

The setenv() can be dropped because the socket location is either the
compile-time default or the already set environment variable.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>