virt-aa-helper: translate error messages

These messages are visible to the user, so they should be
consistently translated.

* cfg.mk (msg_gen_function): Add vah_error, vah_warning.
* src/security/virt-aa-helper.c: Translate messages.
(catchXMLError): Fix capitalization.

cfg.mk

@@ -337,6 +337,8 @@ msg_gen_function += qemudReportError
 msg_gen_function += regerror
 msg_gen_function += remoteDispatchFormatError
 msg_gen_function += umlReportError
+msg_gen_function += vah_error
+msg_gen_function += vah_warning
 msg_gen_function += vboxError
 msg_gen_function += virConfError
 msg_gen_function += virDomainReportError