From Ambari Web, browse to Services > Pig.

Save the old Pig configuration and add symlink from /etc/pig/conf:

mv /etc/pig/conf /etc/pig/conf.saved

ln -s /usr/hdp/current/pig-client/conf /etc/pig/conf

ls -la /etc/pig

total 4
drwxr-xr-x 3 root root 4096 Jun 19 21:51 2.3.0.0-2323
lrwxrwxrwx 1 root root   35 Jun 19 21:54 conf -> /usr/hdp/current/pig-client/conf
drwxr-xr-x 2 root root 4096 Jun 14 00:11 conf.saved

Select Refresh configs from the Service Actions menu.

Select Run Service Check from the Service Actions menu. Confirm the Service Check passes.