whenever bundling, ensure packages downloaded

specifically... for the bundling arch!

also, whenever running the project constraint solver, make sure
that (host) packages exist even if the versions haven't changed!
Add hostname/meteor release/os to package stats
A steaming pile of hacks to get report-stats test passing.
Add a selftest.fail() reason
Fix direct dependency reporting.

And test for it.
Record session id on package stats
Fix bug in `Run.stop()`.

Otherwise selftest crashes if you call `run.stop()` without calling
e.g. `run.match()` first.
Remove obsolete XXX
Do a 'meteor run' in report-stats test.

It tests that stats get sent on 'meteor run', and also is faster than
bundling.
Add 'clientAddress' to package stats meta test.

Currently fails because 'meteor deploy' sites don't have
HTTP_FORWARDED_COUNT set. I think the right way to fix this is to have
the runner set it.
Use `EJSON.equals` in `selftest.expectEqual`