updated ostrich to 1.7.2-beta with experimental upgrade to commons pool 2.2

 updated project to use commons pool 2.2
 updated some classes to not use deprecated methods
 fixed/updated tests
 minor changes, and removed tests per review comments
 added docs re. why ExhaustionAction is removed

Change-Id: I311f63757f7516debd310bc8aee744ae7cd2a522