exempt core generated libraries' owlbot.py files

Author: chingor13

generation/update_owlbot_postprocessor_config.sh

@@ -6,7 +6,7 @@
 
 set -e
 
-for dir in $(find . -mindepth 2 -maxdepth 2 -name owlbot.py | sort | xargs dirname ); do
+for dir in $(find . -mindepth 2 -maxdepth 2 -name owlbot.py | grep -v 'java-common-protos/' | grep -v 'java-iam/' | grep -v 'java-showcase/' | sort | xargs dirname ); do
   pushd "$dir"
 
   # form a perl command to replace java.common_templates() invocation