netinet*: variable cleanup

In preparation for another change factor out various variable cleanups.
These mainly include:
(1) do not assign values to variables during declaration: this makes

the code more readable and does allow for better grouping of
variable declarations,

(2) do not assign values to variables before need; e.g., if a variable

is only used in the 2nd half of a function and we have multiple
return paths before that, then do not set it before it is needed, and

(3) try to avoid assigning the same value multiple times.

MFC after: 3 weeks
Sponsored by: Netflix