Fixed libprocess tests due to the new io::read semantics.

Review: https://reviews.apache.org/r/24772
Cleanup mesos due to the new io::read semantics.

Review: https://reviews.apache.org/r/24774
Simplified a test by using FUTURE_DISPATCH.
Fix for some style issues.

Review: https://reviews.apache.org/r/24773
Removing unnecessary argument (same as default).
Add docker containerizer destroy tests