Explicitly load the config at confd startup

Explicitly load the config at confd startup

Currently, confd main function doesn't load the config, but simply
forks the individual timer threads, which will—as a side effect-also
load the configuration as soon as they start.

However, this makes codes to the startup more complex, so let's
explicitly (try to) load the configuration as first thing.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>