Fix technical debt and reduce lines

Focused on iterating over entrySet along with more fixes for
dead stores, unnecessary exceptions. I'm also starting to work
on reducing the number of code lines.

* Iterate using entrySet
* Remove useless assignments
* Unnecessary exceptions
* Use StringBuilder instead of StringBuffer due to synchronization
* Potential null exceptions being thrown
* Returning a empty collection vs null

Issue-ID: POLICY-482
Change-Id: If6ac8e812237f37b2b10c534535df4090a5073dd
Signed-off-by: Pamela Dragosh <pdragosh@research.att.com>