We had occasional failures, because the fuzz could overwhelm the difference
in routes. Increasing the amount to 2,000,000 millisatoshis makes the
riskfactor 53msat (2000000 * 14 * 10 / 5259600) which is always greater
than the worst-case fuzz of 5% on the fee of 1002msat.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>