BundlesDirSuite.TestGet fails

[Aaron Bentley]

This test fails intermittently, as seen here:
http://reports.vapour.ws/releases/issue/578cdbe1749a5661be60bd59

The failure I observed happend when run with -race, but it does not say DATA RACE, so I believe it is a normal test failure, not a race test failure.

[William Reade (fwereade)]

The test was assuming the charms were being downloaded from the `github.com/juju/testing` HTTP server, and using that to "block" the request that was meant to be aborted; but we're not using the test HTTP server at all, we're getting them from the apiserver directly.

Dropping the concurrency, just passing in a pre-aborted channel: demonstrating that abort is honoured is the critical thing here.

[William Reade (fwereade)]

http://reviews.vapour.ws/r/5281/