Flatten the BinderTransports using the "guard clause" pattern

[jdcormie]

Binder[Client/Server]Transport uses the following "single exit point" style/pattern of control flow all over the place:

if (inState(ExpectedState)) {
  if (!doStep1ThatCanFail()) {
    // error handling
  } else if (!doStep2ThatCanFail()) {
    // error handling
  } else if (...) {
    ...
  } else {
    // Happy case.
  }
}

This has the advantage of a single exit point which, in C-like languages has historically been useful for unconditional cleanup like releasing locks and closing resources. However, in Java with exceptions, unconditional cleanup has to happen in a finally block and so we don't really benefit. On the other hand the single exit point pattern creates a lot of nesting:

• The happy case is always nested at least two levels deep in an else.
• Inserting a new no-fail step in the sequence (say between 1 and 2) is awkward. You have to either create an empty error handling block or create a new "else" clause, increasing the indent/nesting level by one.

In this PR, I reduce nesting and make life easier for future PRs by converting all BinderTransport methods to use the guard clause pattern instead:
https://refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html
https://testing.googleblog.com/2017/06/code-health-reduce-nesting-reduce.html