test_lightningd.py: Enable bech32 test for DEVELOPER

[jsarenik]

Since bitcoind 0.16 is already released it is safe to enable
this test already.

[jsarenik]

@cdecker could you please update docker image cdecker/lightning-ci to install bitcoind 0.16 in order for the bech32 test to pass? Thank you.

[rustyrussell]

Please also remove the 432-block check in test_lightning.py too: we now only need to generate 100 blocks (to get some funds to spend). Might speed up tests a little, too.

[cdecker]

We have a bit of an overlap with #1134 now. 100 blocks isn't sufficient since we need at least one coinbase to be mature to be able to do anything. We also need to fix a few tests that rely on a specific blockchain height.

[cdecker]

I cherry-picked your first commit onto #1134, so this now is completely superseded by it 😉
Cherry-picking will still give you credit for your commit though, which is important to me 😃

[jsarenik]

@cdecker Thanks! :)

[jsarenik]

@cdecker @rustyrussell Closing this pull request in favor of #1134 - though I would like to be included in further discussion regarding 100 blocks...