This commit add 3 integration tests for send-to-route RPC call.
One test ensures that single-hop payments are processed. Another test
checks that payments through a multi-hop route are processed. Lastly,
there is a test to check error propagation while sending payments via fake
predefined route.
In router_test FindRoutes is passing DefaultFinalCLTVDelta in place
where numPaths is expected. This commit passes a default numPaths for
function calls to FindRoutes so that final cltv delta are correctly
passed.
t4sk