Increase time limits in CircuitBreakerMTSpec, see #3243

The test failure was:

    [info] - allow many calls while in closed state with no errors *** FAILED *** (1 second, 66 milliseconds)
    [info] Set(succeed, CBO) was not equal to Set(succeed) (CircuitBreakerMTSpec.scala:52)

That is in the very first, simple scenario, and it can be explained by that it takes more than 1 second for one of the 100 Futures to complete. 

Increasing the callTimeout to 2 seconds should make it less sensitive (well it has not failed in months).