Undo log calls commented out in commit:64cd0fe.
Merge async.series operations without an async mode with those that do.

Some intermediate steps in async.series sequences always completed
synchronously and didn't actually need async support. Sequences were
arranged that way for clarity, but having unnecessary steps in a
series sequence is expensive on the stack.

These steps have been merged down into the following async step, or
merged into the completion function when they were at the end of
the sequence.

References #2035.
Collapse async.series sequences of length 1. References #2035.