Fixed broken POD in Gerrit::Client::Test

Would have been detected by t/pod.t if Test::Pod were installed
on my machine :/
Fix race condition in stream-events

We were invoking callbacks before pushing another read request onto
a handle. If any of those callbacks caused events to be pumped, data
from the handle could theoretically be lost.
Improve timeout behavior in test

Increasing the timeout as done recently won't help if the mock ssh
command itself still exits too fast.

Include more detail in the message so it can be seen how many events
were missed (or if events have been received at all).
Add diags to aid debugging problematic test failures
Prepare release 20140610