smb: apply a whole bunch of static analyzer improvements

Summary:
among other things:

• {} initialize the posix structs
• =default d/ctors where appropriate
• synced argument names between header and cpp
• no c-style casting
• while(true) instead of while(1)
• initialize class members that could previously have gone uninitialized
• no single-line-multi-variable declaration

Test Plan: builds

Reviewers: ngraham

Reviewed By: ngraham

Subscribers: kde-frameworks-devel, kfm-devel

Tags: Dolphin, Frameworks

Differential Revision: https://phabricator.kde.org/D27646