only call avgtool if checkbox is selected

Currently if the set version checkbox is selected, data enters, then uncheck, the plugin still updates Info.plist.  Also when the IPA is created and the version checkbox is selected, but only one field is set, the second value is considered to be blank and excluded from the file name.

This fix checks the boolean before calling the avgtool and always use the Info.plist values creating the ipa name.

See JENKINS-21387 for an example.