Fix findbugs violations in md-sal - part 2

Fix findbugs violations in md-sal - part 2

- sal-broker-impl
- sal-dom-broker-config
- sal-binding-config
- sal-akka-raft-example
- clustering-it-provider

Violations:

- Method may return null, but is declared @Nonnull
- Method with Optional return type returns explicit null
- Method ignores exceptional return value
- Field not guarded against concurrent access
- Unchecked/unconfirmed cast of return value from method
- Load of known null value
- Parameter must be non-null but is marked as nullable
- Class implements same interface as superclass
- Redundant nullcheck of value known to be non-null
- Unread field
- Reliance on default encoding
- Should be a static inner class
- Questionable cast to concrete collection
- Dead store to local variable
- Dereference of the result of readLine() without nullcheck
- Method ignores return value
- Finalizer does not call superclass finalizer
- An increment to a volatile field isn't atomic
- Dead store to local variable
- Redundant nullcheck of value known to be non-null

Change-Id: Iec7205b49a0cbafff33db97c9c753a5425f929a6
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>