Some global variables are patched to shorter values in these tests. But the goroutines that read
them can outlive the test because nothing waited for them to exit.
This commit adds a Wait() method to the routine manager, so that tests can wait for the goroutines
to exit. This prevents the data race because the 'reset to original value' can happen
after all other goroutines have stopped.
The bulk of this commit is moving the LeaderRoutineManager from the agent/consul package into its own package: lib/gort. It also got a renaming and its Start method now requires a context. Requiring that context required updating a whole bunch of other places in the code.
