tests: pull common http server setup out of individual tests There are currently two different tests using roughly the same code to create temporary scripts acting as HTTP servers. As there is going to be at least one more in an upcoming change, factor those out in a standalone dumbhttp.py script.

util: move md5 back next to sha1 and allow to call it without an argument This effectively backs out changeset 908c5906091b. The API change is done so that both util.sha1 and util.md5 can be called the same way. The function is moved in order to use it for md5 checksumming for an upcoming bundle2 feature.

test-bundle2-exchange: do not drop HG_NODE from the hook output HG_NODE is precisely something we would like to test.

obsolete: update test-commit-amend to use obsolete option This test actually used the obs.py file as part of the test, so we need to fix up the test a little more than usual to work with the new obsolete option flags.

obsolete: update tests to use obsolete options The obsolete._enabled flag has become a config option. This updates all but one of the tests to use the minimal number of flags necessary for them to pass. For most tests this is just 'createmarkers', for a couple tests it's 'allowunstable', and for even fewer it's 'exchange'.

obsolete: prevent options from being used without createmarkers exchange and allowunstable should only be enabled if createmarkers is enabled, so check for that and raise an exception if that's not the case.