Packaging guidelines: ScriptletSnippets fixes

[Ville Skyttä <ville skytta iki fi>]

Guidelines change:

http://fedoraproject.org/wiki/Packaging/ScriptletSnippets
The scriptlet snippets page in Wiki has been updated to fix some inaccuracies 
in scriptlet exit statuses and scriptlet termination causes.

Changes:
http://fedoraproject.org/wiki/Packaging/ScriptletSnippets?action=diff&rev2=9&rev1=7