minor readability fixes in preparation for more work on this file:

- replace nested 'if' with '&&'
- fix indentation
- annotate the end brace of some huge block
- remove useless parentheses



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@20597 65c4cc65-6c06-0410-ace0-fbb531ad65f3