Reverted back from Open4 to Open3 due to segmentation fault

The reason of segmentation fault is unknown, but it seems to be
related to Open4 library. So I have to temprorarily revert that.
Merge branch 'master' into AERIE
Updated load balancer on VM migration success.

* Updated load balancer to point to the new URL of migrated VM.
* Logged more info of backtrace.
* Increased the timeout for waiting IP address.