Fix analysis server asynchrony test.

Fix analysis server asynchrony test.

The test had two bugs: it neglected to account for the
"server.connected" notification, and it failed to allow the test to
run to completion before reporting success.  The second bug sometimes
covered up the first, making it look like the test succeeded.

R=brianwilkerson@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41345

[Paul Berry, 2014-10-27 21:53:13]

paulberry@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2014-10-27 22:57:23]

LGTM

[Paul Berry, 2014-10-27 23:19:23]

Committed patchset #1 (id:1) manually as 41345 (presubmit successful).