CiviTest - Fix gitignore for truncate.xml
CiviTest - Remove & don't generate truncate*.xml

These files don't appear to be used:
 * A quick grep for "truncate.xml" (etal) doesn't find any matches
 * Munging or deleting the file doesn't yield any new errors when running a test-suite (CRM_Core_AllTests)
Merge pull request #3310 from totten/master-truncate-xml

CiviTest - Remove unused files ("truncate*.xml")