Fix FindBugs violations and enable enforcement

Fix FindBugs violations and enable enforcement

- Method call passes null for non-null parameter
- Method ignores exceptional return value
- Boxing/unboxing to parse a primitive
- Redundant nullcheck of value known to be non-null
- Constructor invokes Thread.start()
- Load of known null value

Change-Id: I3cf3c48306c1ade906fe51b5c0492f5a669a2d43
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>