IMPALA-1053: only log unsupported type warning once

Change-Id: Ibb34e4632f87ac192bb58d4d6616b41e7dac53d2
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3140
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins