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Fixed flaky FaultToleranceTest.ReregisterFrameworkExitedExecutor test.

Review: https://reviews.apache.org/r/14762
Fixed weights parsing in the master to properly account for roles.

Review: https://reviews.apache.org/r/14766
Disabled ZooKeeperMasterDetectorTest.MasterDetectorShutdownNetwork
due to MESOS-455.

Review: https://reviews.apache.org/r/14768