Fix syntax in test_load_balancer_basics._check_load_balancing

The set == {} syntax is invalid in python 2.6.

Note that even though the test is currently being skipped,
it's interpreted before the skip is executed so this fails
regardless of the skip decorator.

Closes-Bug: #1277951

Change-Id: Ic64622604a717db33555784cfe265e6af3e6dea7
Merge "Fix syntax in test_load_balancer_basics._check_load_balancing"