Cleanup network timeouts and htools imports

This patch removes the last HTools module imports from non-htools code
(the HTools.Types module), but it requires an associated cleanup:
using luxi-specific constants for luxi timeouts (the only effect is
that one timeout decreases from 15 to 10, the default value in the
python code), and moving of the (now) RAPI specific constants to
RAPI.hs (which allows simplifying their type/usage).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>