unskip test_integration_1

Finally the test_integration_1 test became unskipable.
* ssh a machine on neutron is not as flaky as before.
* Attaching volume to a booted instance is not flaky.
* EC2 Image bundle is working again.

Change-Id: I88dd708f1091d7d4ee1d7e03d800f7165f4936a4
TODO: Add stricter response validation.
Merge "unskip test_integration_1"