travis: skip the Fuzzit-Sanity stage when it's run by cron

.travis.yml

@@ -14,6 +14,9 @@ stages:
     - name: Fuzzit-Fuzzing
       if: type = cron
 
+    - name: Fuzzit-Sanity
+      if: type != cron
+
     # Run Coverity periodically instead of for each commit/PR
     - name: Coverity
       if: type = cron