[commons] CloseableServiceObjects needs to keep track of use count

[kriegfrj]

Was implementing #116 and wondering why my test kept failing - resources not getting cleaned up when expected. I think it's because I uncovered a real bug.

CloseableServiceObjects keeps track of services returned by getService() in an IdentityHashMap-backed set called instances. Then on close it iterates through them all and calls ungetService() to release them.

However, I discovered using the debugger that getService() internally increments the use count every time you call it, even if it returns the exact same service instance as a previous call. So really, you need to make sure that every getService() is paired with an ungetService(), and not simply call it once per service object.

Should be an easy fix (on its way).