sanitycheck: fix skipped element in junit output

The skipped element was left empty, fill it with details to make parsers
happy.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/scripts/sanitycheck b/scripts/sanitycheck
index 73fbed5..1f2accc 100755
--- a/scripts/sanitycheck
+++ b/scripts/sanitycheck
@@ -2180,7 +2180,9 @@
                 elif ti.results[k] == 'SKIP':
                     el = ET.SubElement(
                         eleTestcase,
-                        'skipped')
+                        'skipped',
+                        type="skipped",
+                        message="Skipped")
 
         result = ET.tostring(eleTestsuites)
         f = open(report_file, 'wb')